Dig, you really are spot on with your assessment of the current state of mintage numbers and popularity of "certain" coins from the US Mint. It's as you say- some of their releases will do well- especially 1st issue "restrikes" of already popular coins from decades ago (aka Morgans and Peace dollars). Those 2021 issues had a built-in desirability to them and seem to be holding their "values". Most modern commemorative coins apparently do not do the same. As always, the bottom line is that if you like the coin, then consider buying it, but oftentimes it's worth it to just wait, let the initial excitement die down a little, and then scoop things up if you really want to. It takes something really special to get that initial bump in price and maintain it for good.
So, after much of the hoopla has died down and the Mint continues to issue follow-up coins, things have a strong tendency to wane in popularity. I haven't been to a coin show in a couple of months now (waiting for the local September show with Don and AGguy), but I have heard that even the latest 2023 Morgan and Peace dollar issues, which were supposedly offered for $76 directly from the Mint, are actually selling for $80 at some shows- a small $4 bump from original issue price. Definitely worth paying if 1) you're after such a coin and 2) you missed out on it originally. I myself avoided them because I continue to be PO'ed at the Mint for its continuous issuance of what seems to be sometimes ridiculous offerings at ridiculous prices.
And to add to that, the many horror stories that occur on their website when one is trying to order from them. You have some collectors who really just want 1 or 2 for their collection, you have some enterprising individuals who would like a chance to buy a bunch, flip them and profit a little, and on top of that you have some coin dealers who will even pay their customers to buy as many multiples of some coins as they can, and resell them to the dealer so they can resell for even more money. They're all competing for the same coins at the same time, and even though we can split atoms and put men on the moon, the US Mint just can't seem to prevent their website from crashing or freezing. Incredible.
On the other hand, when it comes to AGE's, and I'm speaking specifically to the 1/4 oz. and 1/2 oz AGE's and not their 1/10 or full ounce counterparts, those years where there were lower than usual mintages (especially the 1988-1996 years), they have demanded quite high prices over and above their usual markup, and they're getting them! And although I generally find it foolish to get bullion coins slabbed by NGC or PCGS, it has become so commonplace that when I can find those early issues already slabbed, and can check their authenticity via their websites, with the incredibly huge amount of fakes coming out of certain countries, sometimes I think maybe it's not such a bad thing after all.
I don't know, I'm probably unlike a lot of the forum members here, in that I was a coin collector first, and then also became a stacker. So, I still keep factors such as desirability, eye appeal, and lower mintage numbers rather high in my esteem. I love being able to do both as IMHO, it's the best of both worlds.
Note: IMO, there are still some "sleeper" AGE's that are currently being overlooked, with no telling when they might rise in premium if at all, but here's a few lower mintage issues that can probably be obtained for around the usual price premiums... the 2006, 2007 and 2008 1/2 oz. and 1/4 oz. Add to that the 2012, 2014, 2017, 2018 and 2019 1/2 oz'ers, and the 2019 1/4 oz. All seem to have lower than usual mintages, and if I had my druthers, I'd rather have tubes of each of those as opposed to the more common ones. Of course, in a perfect world, I'd rather have all pre-33 gold for less than what some people pay for modern bullion issues. Working on a set of pre-33 Indians right now.