More mass means higher gravity. Higher gravity requires more speed required to escape the atmosphere. More speed requires more fuel, or more fuel efficiency, or a lighter rocket. We can't reduce the weight of the rocket itself too much because of the materials we're working with. We can't make the fuels we're using much more efficient because that's just the way chemical combustion is. So the only way to get more power is more fuel, which means more weight.

We can currently juuuuust balance the amount of fuel (and how much force that fuel can generate) against the weight required to lift that fuel and the rocket and a payload. The Saturn V was the biggest rocket we could make at the time of the Apollo launches, and we needed every bit of it to get to the Moon. In sixty years we've not been able to make massive advances in rocket tech, so the SLS is very close to the Saturn V in overall specs, relatively speaking. If we're just ahead of breaking even on that now, you can see how an increase in the requirements would put us behind the curve.

That doesn't mean a 50% larger Earth would result in us never leaving it, though. What it would mean is we'd need to come up with better solutions to one of the above variables - better materials that weigh less, more-efficient fuels, or a better design than igniting a ton of fuel and pointing the exhaust at the ground.