the problem here is that it's not hard to screw up the endgame with this pin, so some players just wait it out all the way and hope you hang yourself
agree w/ jeebus, i've done this and it's the least fun i've had playing this game
Ehh, not really. Let's just take a basic setup for this pin: you have 4 Rc and a Masq, they have nothing. You mat all your Rc, play Masq to kill their copper.
T1a: You gain a copper
T1b: They gain a copper
T2a: You play Masq (pass a copper, trash a copper) -> Rc (gain a copper): gain a copper
T2b: They gain a copper
T3a: Mat your Rc, gain a 3rd copper
T3b: They gain a second copper
T4a: You buy a silver
T4b: they buy a 3rd copper
T4a: You have CCCS as your hand, buy a $5
T4b: They buy a S
T5a: You either draw CCCSMasq or CCCMasq5 or CCCS5. The first you most likely will want to play Masq 2x, trash two coppers, and then buy a Silver (so your next hand would be CSSMasq5). The second can be played the same and the third can buy either another $5 or a gold (if your $5 gives any cash), you can also play the 5 multiple times (e.g. if it is something like Butcher or Wine merchant you can rapidly build up an engine).
Outside of exceedingly rare cases once you fully destroy the other guy's deck, you have a HUGE material advantage and are first mover - it is like you have been spotted 6 turns at the beginning of the game. Unless the game is close to 3-piling or you have some easy method of gaining cards (e.g. Alms or Beggar with a discarding pin), you are pretty much never going to make it back from a pin even if the pinner is bad at the end game.
I talk about completely reduced cases, likely buying out all the coppers, because they are easier to map and validate. However if if you just come back with 3C -> S -> whatever you are gaining a stupendous advantage (at least comparable to having the other guy have his Chapel miss the first two shuffles when yours does not). And frankly anyone who can combo up a pin likely knows how to do
something that will win with this sort of lead.