I still love the RPG elements of, for instance, the early Fallouts.
I've also played a bit of TOEE lately which was pretty nice, albeit Hommlet feels empty as hell and why are there even staircases to run up when there will be absolutely nothing inside for 90% of the time?
ToEE
Hommlet was a mistake but the rest of the game is pretty good, particularly from the second floor of the Temple with the elemental priests rivalry.
So don't give on ToEE just yet.
If you get back to ToEE, consider using the Temple+ mod for more classes and races variety, it's a game changer, this and the optional rules.
Colony Ship seems to be right up your alley
C&C, interesting character development and tough tactical combat is what awaits you.
But combat is really tough so you might want to start with something more relaxed.
If you do like Colony Ship, you should consider playing
Age of Decadence and
Dungeons Rats (dungeon rats is pure tactical combat and dungeon crawler like (but with isometric tactical combat)
Dark Sun Shattered Lands (and its sequel if you like it)
It has everything you're searching for, tactical combat, not the most difficult (depending on how much you cheat and multi-class), some of the best quest design and c&c.
Graphics are charming and the music tracks are some of the best in the history of video games.
Prelude to Darkness
Graphics are not good, i'm not gonna lie and it's a bit buggy at times.
But there is a fixed codex version (if you can't find the thread, someone will)
Best quest design and c&c ever made.
Interesting character development.
And tactical combat.
The game is an acquired taste but the quest design is just
spectacular.
TLDR
For pure and great tactical combat:
Dungeon Rats
Knights of the Chalice (KotC) and
KotC 2
For the same + exploration :
Hearkenwold + KotC 2 (Adventure module made by our resident hero, Dorateen,
available on nexusmods)
For c&c, and tactical combat
Age of Decadence
Colony Ship
Prelude to darkness - It's not for everyone, you should start with something else.
Exploration + c&c + tactical combat
Dark Sun: Shattered Lands and then
Wake of the Ravager.
Underrail - single character, exploration doesn't always mean great exploration, it's good but not great in my opinion.
So here's my advice.
Come back to ToEE + Temple+ first.
Or start with Dark Sun Shattered Lands.
And then it depends if you like tough combat or not, if you do, head towards Iron Tower games (Age of decadence, Dungeon Rats and Colony Ship) and Knights of the Chalice 1 & 2 + Hearkenwold.
If you don't, maybe try Rogue Trader with Daring or lower difficulty.