I'm with you on that setiment. I had been considering the same combination, but am now rethinking that purchase.
I picked up an unopened 21.5-inch 4K UltraFine on Ebay last Summer, for half MSRP, expecting it to be a "stopgap" before Apple released a new consumer grade monitor. However, I was expecting Apple to use something better than the seven-year old panel that has been in the 27-inch iMac. I don't need the added size, I'm more concerned with "Retina" density and would have liked 120Hz and mini-LED, so I don't see a reason to do a lateral move with the Studio Display. Plus, I'd spend the extra for the nano-texture process, adding additional cost. For me, it just doesn't make logical sense to switch, since my LG is working fine without issue.
That's the conundrum, there isn't a good answer to that. If you're like me and want ~219ppi then there's not much to choose from. There's the discontinued 21.5-inch UltraFine, the larger 27-inch model, and the Studio Display. Everything else is primarily targeted toward the PC market. You could try to get a 4K UltraFine off of Ebay like I did. (It's very hard, but not impossible to get a new boxed unit.) LG says that they haven't canceled the 27-inch UltraFine and plan on continuing sales once component shortages ease. The price for the LG is almost as much as the Studio Display, so I'm not sure it's worth saving a bit by going with the LG.
Hence, my advice is to do the same thing I am currently planning: wait until after WWDC. Display analyst Ross Young is still predicting that Apple will launch a device using a 27-inch mini-LED in the coming months, and he states that multiple sources in the supply chain have confirmed this. Assuming he is correct, there is no telling if it is for an iMac, a replacement for the current XDR, or something else that may fill a different part of the product line. Given that it is mini-LED, it will certainly cost more than the Studio Display, but that's probably the most that we can surmise, at this time.
So, unless you need that Studio Display to go with a Mac Studio immediately, I'd wait another three months, if possible, just to keep your options open.