Also, the card touches your discard pile before being topdecked, so you have to figure out all the lose-track fun.
None of those cards are in base or Intrigue, so this only comes up when you're playing with later expansions.
If you wanted to pick a card that is more advanced/more difficult to master than the first expansion is "supposed" to be, I would go with Lurker. That one is a mind bender.
If you wanted to pick a wordy card that is difficult to comprehend on first glance, I would go with Diplomat.
Or for both of these, if you include base 2nd edition, maybe Sentry is a bit too complex there.
Replace does have a lot of words, but it's just a Remodel+, so if you already understand Remodel, you just have to learn the extra part.
Also, Replace works great with the dual-type Victory cards, especially with Mill costing 4 replacing Great Hall costing 3. If you want, you can go Estate -> Mill -> Harem/Nobles -> Province, doling out curses each step of the way. So it's a good fit in that way.
Finally, if you consider Replace as, uhh, replacing, Saboteur, you haven't really changed the wordiness level of the expansion at all. (And there are clear parallels. Replace is a +$2 remodel for you, Saboteur is a -$2 remodel for the other player(s). Both are attacks that can make your opponent's deck worse.)
If I had to criticize:
It does mean Intrigue has 3 attacks that give out curses, but at least they are all conditional or optional so they don't usually run the curse pile down too quickly.
Upgrade in the same set also does the whole trash a card, gain a more expensive card thing. It plays differently enough, though.