1) Provinces can clutter up your deck a lot, especially if you end up having to buy Duchies towards the end of the game as well. If you're not experiencing this, you might be greening too late, not trashing enough, or otherwise building your deck inefficiently.
2) I assume that your idea is to nerf engines so that it would be less often the case that an engine is obviously the best strategy. It would indeed accomplish that, but the problem is: if that's less often the case, something else has got to be more often the case to make up for it. That something is not the boards where it's non-trivial to decide between an engine and a non-engine strategy (like I believe you're hoping) because with the existing rules, we already have boards where the engine components are technically there but it's just obviously not worth it to build the engine. Therefore, some of the obvious engine boards would become non-trivial, some of the non-trivial boards would become obvious big money boards, and the net result is that you're just trading engine games for big money games. Because of their higher complexity and lower reliance on RNG, engines are some of the most interesting strategies to play in Dominion, and therefore the nerf would only serve to make the game less interesting as a whole.
This specific nerf in particular, I imagine, would not even do all that much to make engines weaker. You would still build the engine, and mostly it would work the same way it usually does, but you would slightly more often get screwed by drawing your cards in the wrong order by random chance. This doesn't make the game more interesting, it just makes it more frustrating.