Where do I go after completing the core loop?

I've been working on my project for a couple months now - I've been a software developer for 20 years and have dabbled in game dev stuff before - but I've never really done much of anything before now.

I tend to approach development in a very 'linear' fashion - the game should start with a title screen so get that working first. The game needs a save/load system so get that working next. Once in the game a player needs to transition between maps so I need two maps and a transition point. So on and so forth.

I've gotten to a point where I think I have a rough implementation of everything:

1. Title Screen

2. Persistent settings

3. Saving/Loading games

4. Pause menu with settings/reset/save/load/title/quit options

5. Player loads into a hub area

6. Player can talk to NPCs and choose dialogue options

7. Player can transition to a dungeon

8. Dungeon has a minimap, a few collectibles, and enemies.

9. Player can attack enemies - enemies have health bars and die at 0 HP

10. Enemies can attack the player - player has a health bar and dies at 0 HP

11. The dungeon has an exit and takes the player to the next level of the dungeon or out to the hub.

The thing is - I think that's all the core mechanics in my gameplay loop resolved and I'm not sure what to do next. My core loop functions but everything is terrible (as expected at this point). GUI is ugly, environments are ugly, animations are sloppy, combat is basic, saving/loading is functional but doesn't track everything yet, enemy variety consists of 1 thing with a single attack animation, and story/dialogue consists of NPCs saying things like, "You have talked to me."

I have tons of notes and plans for everything - I know about 80% of what I want to do with things - but I can't figure out what order to do them in. Do I work on non core parts of the loop? Do I pick an area at random to start improving upon? Is there some rhyme or reason to which area I should start improving upon next?

My gut instinct tells me to start leaning into the core gameplay (movement/combat mechanics) but even then - what first? Cleaning up animations? Non core gameplay elements that are relevant (stats, upgrades, etc.)? Or do I simply start working on controls that create the gameplay 'feel' that I want and fix up animations later?

Opposing the instinct to work on core gameplay is the thought that it's going to be difficult to refine gameplay when my environments are so static - without environments that match the expected play area how will I know if my gameplay works for them?

On the other hand something I've been putting off is learning how to do shit with blender. I'm terrible at the 'art' side of things and am using a lot of asset packs and the like for things but am at a point where being able to do things like 'put clothes on a character' would be useful.