Howdy - I'm using RDM (Retina Display Manager), have since I got my first Retina system when they launched in 2011 or so. It works with the MacBook M1 Pro 16", the maximum resolution I get is 3456x2234. I don't expect it to continue to work after Intel processors are phased out, I hope that the author (on GitHub) updates it for M1. I'm also considering forking it and/or join the project as a contributor, because no, you aren't the only one who feels short-changed by the HiDPI resolutions. They are a waste of screen real estate. Cheers!

One more thing re: RDM -- the software figures out the available resolutions from the hardware configuration, screen dimensions, etc. I like 2560@1440 (same as my Thunderbolt display), but in the MacBook M1 Pro 16 it's not available. I use 2560@1600 as the closest resolution to what I'm used to. Cheers!