I swear it doesn't get this hot in other games

The game is horribly optimized to be honest. I remember playing the old Pocket Edition on Galaxy S3

It just has an absolute ton of calculations to perform on hardware that is not made for it.
- Then why did it run just fine on 10 year old phones? Its not like they added any groundbreaking new stuff.
- Minecraft is despite that a horribly unoptimized game that could run fine on A LOT more hardware but has given up on even trying to do so.
  
  There's so so many things they could easily do especially with how big of a game it is, but they just do not.
Has the game changed at all between then and now?

Just wondering if new stuff has been added that takes more resources.
- Every edition that isn't the Java edition has been merged into one edition that cross-plays with every other edition. Pocket Edition is the same edition as every console port as well as the Windows 10 native version.
Omg dude my pretty small (limited) alpha world had the BEST sphinx ever! (On Galaxy Note3)
Well it takes my Xbox one (vanilla) like 10 mins to load, so…

Have you tried ~~our Lord and Saviour~~ Minetest?

It can be a bit rough around the edges, and I can't compare it to Minecraft, but my mid-range phone runs it at a stable 60 FPS without breaking a sweat.

If you install the "MineClone2" game from within Minetest, the gameplay is quite similar to Minecraft, too.

It can't connect to real servers and load Java mods, can it?
- As the other guy said, it's not Minecraft, and not trying to be compatible with it, so no. There's some hacky scripts for converting Minecraft maps and texture packs, but that's about it.
  
  Minetest does have a surprisingly active modding scene of its own, so if you're open for a different experience, I do think it deserves a look. And logging onto a Minetest server is a great way to discover lots of mods, as the client will automatically download and apply the mods from the server.
- It's not Minecraft, so no. But I do wonder if it would be possible to make them cross-compatible somehow?
I did, a few years ago. But I only play MC Java on PC anyways, I just like to boot up bedrock on my phone a few times a year 'cause I'm bored.

unrelated, but my dad's iphone SE (1st gen) used to almost burn the house to the ground when playing hill climb racing.

Java Minecraft*

I feel like Java edition would run better on mobile with sodium installed
- Pojavlauncher is a thing, though it seems to be intended for use with older, pre-sodium MC versions