I can understand the skepticism, but if helps things up at all, I would clarify that I think exceedingly few people who use random tables (even all the way back to the 70s) really use them as a final say in what's happening next. Most who use it probably appreciate it more as a way of dislodging tired tropes and tricks they find themselves always falling back on.

I think of it as one more source of inspiration to keep in your toolbox, alongside the evergreen "steal from media you like." That said, ymmv as with all things in life, and the best prep is the one that works for you!

See, in my campaign I do what you're talking about with regards to mashing ideas together. I just use ChatGPT to get a detailed description of a room/character and to help me to plan out how I ought to glue the ideas together in a way that fits my setting/theme. Sometimes it even adds additional influences to the mix to make the idea seem more embedded in the setting and original.

If you just use it on the prep side, you maintain full editorial control, and you can reply to its bad ideas with "let's do it more like this:" and it'll revise its descriptions/ideas to match.