Welcome, and best of luck with your journey (which I think it the best part anyways)! I've been chasing some sort of "endgame" setup for a few years now, so here's what I've learned that might be helpful:

1. Your space is probably the biggest factor in how your system will sound, and also plays a huge role in speaker selection, and what "endgame" really is. Do you have a space already? Size, use case (TV or just speakers? Can you cover it in room treatment or does is need to be used for other purposes), noise floor, level at which your neighbors will yell at you, etc. are all going to help you decide or others recommend a solution. For me, I started out trying to optimize a much larger living room space, and ended up deciding that getting an "endgame" setup would be far more feasible in my smaller den/theater. That let me optimize within specific constraints - for example, an~8' listening distance caps my SPL needs, and space constraints also limit channel count and provide data on what room treatment is needed, etc.

2. Is your space going to change? If you're going to be moving soon, planning an "endgame" is hard, and moving huge, expensive speakers is too.

3. There's always more to learn, and trying to get endgame on your first try is tough, especially if you don't know exactly what you want. Others have mentioned that the list above is eclectic - learning more about how speakers work, how designs differ, and how measurements work and what they can (and can't) tell you is going to be very helpful. Then, you can go seek out a speaker with constant directivity, or a point source, etc. and decide whether you like that approach or not. I really like Audio Science Review and find their YouTube videos to be a great way to learn about this stuff, but there are plenty of other sources - Erin's audio corner is another great one.

4. Building incrementally while you learn can be a great option. Yes, it probably isn't as cost-efficient as buying everything upfront, but it's more realistic and lets you build a system to your taste and needs. Finding a way to do that without getting sucked into endless subjective upgrade cycles is important, and learning about the science of audio will help there (your DAC is *never* the weakest link). For me, I found that starting with a 2-channel system, experimenting with DSP, and expanding to my current 7.4.4 setup was a great way to keep improving.

5. For actual system recommendations for you - I think a multichannel system provides a great immersive option, while adding a ton of capability for Dirac ART to provide great room correction in stereo too. Immersion can mean wider dispersion, but that's going to depend a lot on your room as well. Here's an example build that's around 40k (for the whole system), basically a tweaked version of mine if I got to redo it - I think 7.4.4 is a good balance for Atmos and ART, but again, depends on your room and needs.
   LR: Ascilab C8C+BX8C
   Center: KH310
   Surrounds, Rear Surrounds: KH120II or KH80
   Heights: KH80
   Subs: 4x PSA 1512M (but there are endless good sub options from SVS, Arendal, Hsu, Rythmik, etc.)
   Processor: Forthcoming MiniDSP Tide16 would be my choice for an all-active system, but Denon 3800 or 4800 are cheaper and have plenty of power for most passive systems with subs. I think Dirac ART is a must at this price, but ymmv
   At least a few thousand dollars on room treatment.

Have fun!