Let me ask you a simple question: Have you played Red Dead Redemption 2 and if yes, how much did you enjoy it?

My point is that GTA IV is kind of the Red Dead Redemption 2 of the GTA series. It is a relatively slow, deliberate game, kind of depressing and unique in its tone, but also very colorful if you look deeper. It's a well-written, incredibly coherent world that you can fully immerse yourself into and still discover new things about after years of playing it, but it's also not for everyone.

The driving physics for example are deliberately heavy, contrary to the arcadey physics the rest of the series is known for. They are the equivalent of the slow animations of RDR2. You're not supposed to have an easy time dodging traffic and sliding around corners, because you're meant to slowly getting used to driving in a strange environment with strange rules together with the protagonist as he's trying to find his place in the absurd, but kind of not realistic persiflage America he found himself in. It's actually meant to take hours for the player to get comfortable with the driving. The driving physics aren't even realistic - cars have ridiculous mass and overlong braking distances - they are hyperrealistic, exaggerated to the point of absurdity, just like the entire setting of Liberty City.

This aspect alone shows that GTA IV has very experimental aspects to it, aspects that go against player's expectations, against what they want from a GTA, because the developers valued tone, atmosphere, narration and, crucially, ludonarrative consistency over pure and simple fun. In some ways, it's a huge success in this regard, but in others, it's an inevitable failure, a dead-end, a decision they almost entirely reversed with the sequel, which is far more of a San Andreas 2.0 that merely uses the technology of GTA IV (albeit simplified and toned down in many respects) while ignoring its rather groundbreaking attempts at unifying gameplay and presentation, only fixing the one glaring dissonance the series suffered from by introducing Trevor as a playable character who can go on wild rampages without breaking character.

I'd argue that it's very much worth it pushing through, but don't force yourself if you never get in the right mood, that is, don't expect it to be continuous, lighthearted fun in the traditional sense, like the rest of the series. Here's my recommendation: Just walk around for a bit, not doing any missions. Take a train ride without a clear goal, soak in the atmosphere, observe people, watch some TV, surf the game's Internet, call a few phone numbers, experiment with the features of the phone you're given, and just explore, do some sightseeing. Perhaps notice, while you're doing this, how every single building is unique and realistic, fitting its environment perfectly, how much the city changes over the course of each day, how surprisingly interactive and logical everything is. Consider treating it less like a game and more like a place you're visiting.