Just a few suggestions, hard to know precisely the best approach, though:
Try a different stain: If the MinWax gel stain you're using isn't producing the desired results, consider trying a different type of stain, such as an oil-based or water-based stain or a different brand of gel stain.
Apply more coats: If the blotchiness is due to insufficient stain, try applying additional coats until you achieve the desired color. Be sure to let each coat dry completely before applying the next.
Sand in between coats: If the blotchiness is due to an uneven stain application, try sanding the surface lightly between coats to even out the finish.
Consider using a pre-stain sealer: A pre-stain sealer can help prevent blotching and promote an even application of stain on softwoods like pine.
Apply shellac: As you mentioned, applying a thin layer of shellac as a sealer before staining can help produce a more even and darker finish. When using shellac, it's important to follow the manufacturer's instructions carefully, as it can be brittle and prone to cracking if not applied correctly.

Espresso stain is notorious for being tough to get an even coat with.

Try a water or oil based stain too.... The gel stuff is kind of "gimmicky".

It's probably not pine and is a hardwood that doesn't need conditioner. Are you sanding higher than 200 grit?

It doesn’t look blotchy to me. The darker and lighter shades seem to start and stop with individual boards. If it was a commercially produced table it’s possible not all of the pine came from the same source in which case you can’t really tell how much it will penetrate individual unique boards. I’ve made some basic furniture with pine I’ve bought from a big box store and was able to stain it successful. Likely all the boards came from the same batch.

How much it penetrates depends a lot on which type/brand of stain you bought, how you applied it and how long you waited before wiping it off. With a large piece it can take a bit of practice. If you’re applying it by hand with a brush on a warm day it can start to dry on the parts you started with before you have a chance to come back and wipe it off, hence it comes out too dark. It can also be the opposite. You might brush it on and end up wiping it off before it has time to penetrate hence it ends up too light. The instructions on the can are highly dependent on heat and humidity.

I would try and do another coat and time it so you know if you need to go longer on a third coat.

And how do you know it’s pine? It looks more like a type of oak. The little indents seem to be a lot darker as if the stain set into those parts. I’m no expert but the grain just doesn’t remind me of pine.

I kind of doubt it’s pine; the long little speckles suggest and open-grain hardwood, though the stain makes it hard to determine the species. I’d suspect oak or ash, though the grain doesn’t quite look right for either. If it were pine, I’d expect to see some gouging or dents in a pine table, since pine is so soft. And even with wood conditioner, pine is really difficult to stain, especially dark colors. This would be about the best stain job on pine I’ve ever seen. I’ve done a little experimentation with undercoats/pore sealers for staining blotch-prone woods, and I’ve found wipe-on polyurethane to be the best. Two thin coats of that work reasonably well under gel stain on pine - better than wood conditioner, varnish, and other types of polyurethane. It might work for you here as well, though you’ll still want to at least scuff sand the surface with 320 grit or higher for the poly to bond.

I would try a dye stain if the gel isn’t getting you the results you’d like. General Finishes Espresso will get you the results, but you’ll likely need to use a bit of the extender if you’re not spraying the finish. If you opt to hand apply and not use the extender, be prepared to almost immediately start wiping off the stain since it will dry rapidly on the wood. Also, ship the conditioner. While helping prevent blotch, it stops some of the stain from absorbing into the pores.

It's not pine. It's "plantation hardwood", aka rubberwood trees that no longer produce enough latex to keep them alive and so they're harvested for lumber.

The stain you have looks like a good start. I would suggest a tinted top coat to even out the colour. Minwax Polyshades is a product that I have used with excellent results even on woods that are difficult to stain evenly. Good luck.

It looks to me like you still have some of the old finish in the wood. Whatever it is just sanding may not get it all out if it's deep in the grain. What does it look like underneath? You may have to try some type of stripper first.

Great question, I'm truly not certain about this. I tried looking it up once I sanded it down, and the color/texture reminded me of pine, but I'm no expert whatsoever, so it may very well be oak.

I'm glad that you don't think it looks blotchy! I am probably being a bit too overzealous with wiping. When I tried this stain previously, I took the opposite approach and it ended up looking tacky. I need to keep working on finding that happy medium. Thank you for your advice!

Thank you very much for those excellent tips!

I did for my final sanding. I went over the top with 400 grit to make it smooth. Should I have kept it at 200?

You're the second person to mention oak, so I suspect that's correct. I like your idea of wipe-on polyurethane! I can handle scuff sanding, I just need a break from the power sander for awhile 😅. Thank you for your advice!

Not even remotely close to pine. It's 'rubberwood', 'acacia' or whatever catch-all term they use for generic import hardwood.

The key issue is surface prep and finishing method. First, your sanding isn't even. Whether you haven't gotten the original finish off, or we're seeing bits from your previous attempts, you can clearly see how the surface varies across the top and especially the side profile. Going this dark with stain alone is extremely demanding in terms of surface prep. There are also fundamental limits to how much stain different woods will accept.

Shellac will help with evenness, but not with darkness. The opposite, in fact. But that's not a bad thing.

What you need here, if you insist on a dark finish with wood that doesn't want to go dark, is to do what the factory did: tint. They don't stain, they use tinted finish (toner) to get the color in the finish itself, not the wood. Then the wood doesn't matter, it doesn't matter that they used a grab-bag of scrap hardwood that never matches, you just tint it to hell.

Problem with this, and a fundamental problem people have refinishing commercial furniture, is that it's not easy to use toner. You can't apply it by hand without getting some streakiness. It has to be sprayed. What you can do, however, is find rattle-can toner. See if there's a Mohawk dealer near your, or consider ordering some. A couple cans should do a top like that.

Watch some pros if you need to understand more about how colorwork is done: John's Furniture Repair and Tom Johnson Antique Restoration

I had a really difficult time with a piece of maple because it has a very tight grain structure, which makes it difficult to penetrate with stain. If this is maple and not pine, it could be part of your problem.

Yeah 200 is high enough.

Interesting! I've never heard of that, but it's good to know.

Thank you for your input! Is there any chance I could get away with putting the dye stain over my existing stain, or would I need to sand it off and try again sans conditioner?

Thank you, this is reassuring! 😊

Thank you for all your input! Can I use Mohawk toner over my existing stain, or will I need to sand it off first? Also, can I put a finish on top of the toner once it sets?

Compatibility is a complicated issue. Their toners are based on a precat lacquer AFAIK. They should be alright on a fully cured stain or finish, but you can always ask the manufacturer, being sure to specify what you've used. A coat of shellac will often solve compatibility issues. As for top coating, they sell rattle can pre cat lacquer that you should use, in the sheen of your choice.

Thank you for clarifying! I really appreciate all your help 🙏