I disagree, I think TUIs are a great fit in some problem domains.
Think for instance the Debian package configuration dialogs -- they're far more comfortable than the same questions without a TUI, and still work over a serial console if you have to use one.
For tools like various kinds of "top", there's many potential tools you can use to the same end and intentionally using one that draws CPU graphs over one that just displays a number. Graphs are much easier to interpret than a column of numbers.
In many cases they're the optimal choice given some constraint -- like the desire to have minimal dependencies, working over SSH, and being usable without breaking the flow. Yeah, you could make a tunnel to a tool that runs a local webserver and delivers graphs by HTTP, but the ergonomics of that are terrible.
Sure, I said I understand why people build them. I’ve used a lot of them. And yes with the tools we have you’re right, but I’m more lamenting the wonky, kind of archaic, unintegrated, only-semi-composable toolset that we have. No fundamental reason why you couldn’t deliver more structured UIs directly over SSH or a serial console, it’s just that in this timeline that didn’t happen yet (apart from X forwarding, which isn’t quite what I’m on about).