Super Smash Bros.

It will get loose, but only after a year or so of frequent use. If you smash very, very often (eg. you use Kirby), you may want to change up your game a little. You could buy a third-party controller, as theirs tend to be more durable (but rarer).

And yes, at least one smash per character is vital or at least very useful. If you have a messed-up control stick and can't smash, you'll have some trouble playing to full potential. If by progress you mean 1P mode, then don't bother smashing. You can beat computers without smashing at all, as grabs are almost as powerful (except on Kirby).

I have a controller that requires a huge amount of effort to smash with, yet it works perfectly for games like Banjo Kazooie.