Tenured researchers shouldn't be teaching, IMO. They can be doing research full-time, and leave teaching to those who care to teach. I, personally, dislike research, but I would love to become a CompSci professor and teach the next generation of software developers and technologists. The problem is, I do NOT want to do research. Give me a Master's in CS with some sort of "teaching extension" on it and I'll go teach and the researchers can go do important work researching!
Edit: for the upper division courses, researchers certainly should have some involvement, I agree with several of you on that point!
My university had lecturers that were precisely this (masters in CS, focused on teaching intro undergrad courses).
However, I think there is still a lot of benefit from having researchers teach upper level courses. Firsthand experience in research brings an additional dimension that can be appreciated by students who are beyond the introductory level.
There are also tenured professors who are good at both research and teaching!
I believe that this is yet another case of middle ground being the best: leave the bulk of teaching to specialists, but keep the research professors doing courses close to their actual field. Don't underestimate how educative teaching can be for the teacher. But this is certainly no big insight. Or are there places that do not, at least to some amount, do it like this?
The big problem is that the teaching faculty are paid like absolute garbage and have no job security or continuity between semesters. They are widely abused by universities and often are paid at or below wages you'd get working the cash register at Target.
You may be confusing adjuncts, which are part time temporary features, sort of line substitutes; and teaching faculty, which are full faculty members without research responsibilities. They are certainly paid better than Target cashiers.
I agree with your point that upper division courses need researcher involvement, but please try to be less rude about how you say things. This is a comment thread, so there’s no need to act like that, you could make your actual point in a nicer way and I would have seen it like the commenter above you and agreed that I overlooked this case. have a great weekend.
Edit: for the upper division courses, researchers certainly should have some involvement, I agree with several of you on that point!