Much more storage space

Much more storage than 512GB?

a higher-rez 120hz screen (beautiful)

Much higher res than 2160x1080? And Is the difference between 90hz and 120hz really that noticeable?

cameras that rival my DSLR but take MUCH better low light pictures (cats)

I'm sure other devices already had cameras just as good, but for the comparison I'm going with I'll grant that it's very likely your new phone has a better camera

USB-C

Almost every phone was USB-C 6 years ago

more speed (I didn’t need more speed, but it’s nice that it’s there)

Probably the only number that would be extremely higher on your new phone is a benchmark for speed, which probably won't mean much unless you're a heavy gamer on your phone, and even then most games try to hit a wider audience so they have lower specs.

absolutely bonkers battery life

Much more than 4000 mAh?

So, let's forget the camera and benchmarks for a second, compare your phone with this: https://www.phonearena.com/phones/Asus-ROG-Phone_id10914 which you could have bought 6 years ago for $900 and tell me if your new phone is really that much better or cheaper. Then let's do the same with an extra 6 years, so find me the best smartphone you can from 2012 and see if it's even comparable, and if you go back 6 extra years there weren't even any smartphones. And that's the whole point OP was making, your new shiny phone is great, but you could have gotten a very similar thing 6 years ago when you bought your previous model, you would still be wanting to change it now because that device would not have received updates and the battery would probably have started to lose it's charge faster, etc, but technically phones today are not that much better than 6 years ago, especially not considering the amount of advances that happened in the 6 years prior to that, or the 6 before then.