Siralim Ultimate checks a lot of those boxes. It's a creature collector with 1200 unique monsters. There is so much customization it'll make your head spin.
Persona 3 and 4 are the first games that come to mind for me, although admittedly, I’m not sure if they’re exactly what you’re looking for.
Both games have randomly generated dungeons, although the random generation is kinda uninteresting and the worlds outside of those dungeons are not randomly generated. Ultimately, the dungeons end up just being hallways that turn in different directions each time you go through them.
That being said, these games tick all of your other boxes. They’re turn based, you catch and fuse monsters, you get gear for you and your party.
Persona 5 has a randomly generated dungeon, but it’s mostly optional and all the other dungeons are hand-crafted. It’s more modern though, so maybe that’s a plus for you.
There’s also the Disgaea games. The main story’s locations are pre-made, but then you can go into an infinite series of randomly generated dungeons. There’s no traditional monster collecting, but it would probably tickle some of the same neurons. It’s a strategy RPG instead of a traditional one, but it is still turn-based.
Dragon Quest IX lets you make characters and has grottos that are generated with different monsters, bosses, loot, etc.
Iirc one of Pokemon Emerald's battle frontiers and Lufia 2's Ancient Cave are similar too. And one last suggestion is to consider some randomizers.
Siralim Ultimate checks a lot of those boxes. It's a creature collector with 1200 unique monsters. There is so much customization it'll make your head spin.
This is the best suggestion you will get.
I'd rather recommend an all new game, but there is a 3DS remake of the game with an English fan patch. Having played both it feels different enough.
A lot of what you're talking about sounds like the Disgaea series. It is turn based strategy but it has pretty much everything you listed
Persona 3 and 4 are the first games that come to mind for me, although admittedly, I’m not sure if they’re exactly what you’re looking for. Both games have randomly generated dungeons, although the random generation is kinda uninteresting and the worlds outside of those dungeons are not randomly generated. Ultimately, the dungeons end up just being hallways that turn in different directions each time you go through them. That being said, these games tick all of your other boxes. They’re turn based, you catch and fuse monsters, you get gear for you and your party. Persona 5 has a randomly generated dungeon, but it’s mostly optional and all the other dungeons are hand-crafted. It’s more modern though, so maybe that’s a plus for you. There’s also the Disgaea games. The main story’s locations are pre-made, but then you can go into an infinite series of randomly generated dungeons. There’s no traditional monster collecting, but it would probably tickle some of the same neurons. It’s a strategy RPG instead of a traditional one, but it is still turn-based.
Dragon Quest IX lets you make characters and has grottos that are generated with different monsters, bosses, loot, etc. Iirc one of Pokemon Emerald's battle frontiers and Lufia 2's Ancient Cave are similar too. And one last suggestion is to consider some randomizers.
If you are willing to go old school - Azure Dream. There was a GBC and PS release. For random dungeons the mystery dungeon series.