I'm hand-painting all of the textures for the land, structures, and setpieces as I progress. I have an atlas of textures in Ultima VI, re-created by me for all the props and setpieces, and now I'm working on foliage for testing a biome scatter script, and the first biome is going to be a Mixed Temperate forest, which I've researched and tried to distill into a few trees, bushes, shrubs, flowers, and other things you'd find. The video above shows my process in Paint Shop Pro X9 that I use to make all my textures. I use a mouse to do this since getting out and fiddling with a Wacom tablet is too much extra complication. I'm atlassing the textures to improve performance in Unity by reducing draw calls.
I don't actually object in principle to using generative tools, but I really enjoy hand-crafting the textures, and generative tools should be for helping us to get the miserable parts out of the way, not the fun ones. Also, I haven't found a generative texture model that looks right to me. I have a very particular vibe I'm going for, and even asset store assets just won't do since I don't want to restrict the aesthetic, as I want to see what it can become without boundaries.
The only textures I currently foresee potentially using generative tools for is the character textures, since Ultima VI has 200 npcs, and my game #NotSSgame has a big 'ol bunch of npcs as well. Hand-crafting NPCs properly would take a week or two PER character, which is simply not viable at this juncture. So generative tools on that front may be handy for getting the game up and running, though if I had the money to pay artists to make these textures, I would prefer that. Only time will tell if character textures are viable to do hand-painted. I foresee making basic ones generatively, then going in and making proper models/textures as I can with characters descending in importance, selling the difference in visual quality as a kind of "character bokeh" - less important characters are less detailed, which is already standard practice in game development, anyway.
But anyway, for now I am enjoying slowly learning the craft of low-res texturing, a little too high-res to be pixel art, and not so high frequency that it looks busy, going for a mix of Wind Waker and PS1 textures like Mega Man Legends. I'm still developing the style as I go.
