The Curse being worse than a Copper doesn't matter so much given that there's a cantrip trasher in your deck so the Copper would likely just be getting trashed the next time you draw it anyway.
That's not a given.
Firstly, you need to get the Curse and the trasher to collide. And until then you're down $1 spending money each time you draw the Curse instead of a Copper.
Secondly, every time you trash a Curse, you're forgoing the opportunity to trash something else. Granted, you'll
try to prioritise trashing your starting Estates and the Curses you've given yourself over trashing Copper, but my intuition is that you'll find yourself inconveniently at the mercy of shuffle luck.
Thirdly, given the Curses are going to run out quite quickly, you do need to be a little careful the game doesn't end on piles before you've managed to trash them.
As an afterthought, hasn't Chapel demonstrated that it's pretty hard to wreck the game by having too much trashing available, too cheaply? This card is
only a cantrip trasher/Curse gainer.