My issue with TUIs is the lack of a simple interaction model. Every tool invents its own navigation style like vim bindings, custom key combos, mouse-driven flows and there’s no common fallback. In GUIs, the mouse is always there if nothing else. Even basic things like tabbed navigation can become confusing in TUIs sometimes

Sure, for a lowest-common-denominator, GUIs and websites will let you use a mouse. That's great for if you want to use a tool & don't want to take time to get familiar with it.

There are some things which are inherent to GUI or CLI interfaces.. but, overall, nothing ensures a TUI will be good, and nothing prevents a GUI from providing a good interface. -- The distinctions are generally going to be program specific.

So e.g. using openlens (GUI) vs k9s (TUI) vs kubectl (CLI).