There was also many episodes where that was not the case. You're right about DS9. It was entirely an ensemble. Even recurring characters like Garak or Nog got loads of screentime. Maybe it was less the case for Voyager or Enterprise due to the writing or lack of decent acting for the cast.
In TNG you got episodes every season where it shifted the focus onto a different main character. Almost everyone got their turn per season, and sometimes more than once. So you'd get an episode with the focus on Beverely Crusher, or Counsellor Troi, or Wesley Crusher or Worf or Data or LaForge etc. Sometimes the Captain and First Officer might barely play, or sometimes as much as in they did in this episode of the Orville.
Occasionally you'd also have the focus on supporting guest characters like Lieutenant Barclay, who was also addicted to being in the holodeck (but because he needed to escape from the real world as he didn't know how to interact with people out there - it wasn't a porn addiction).
Same thing happened with Voyager. One episode might be on Tom Paris or B'Elanna Torres or Harry Kim or Seven of Nine or Neelix or Tuvok or The Doctor etc.
And they did the same thing with Enterprise too with one taking centre stage while others either supported or barely played at all in that episode.
None of course were to the same extent as DS9, but all were about on par with this episode of the Orville.
It was only in the original series where the focus was on Captain Kirk, Spock, McCoy and sometimes Scotty each week to the exclusion of others like Sulu, Chekov or Uhura.
And also Star Trek Discovery isn't really as much of an ensemble show like TNG, DS9, VOY or ENT. The focus is almost entirely on Michael Burnham (who isn't even the Captain) and there's never an episode where it shifts focus to one of the other characters. That's one of the things I didn't really like about STD - the lack of ensemble where we didn't get to know the other characters as much as we would have in the other Star Trek shows.