My understanding is that the problem with 'spin gravity' is that unless you are talking about enormous truly enormous space stations, then the human vestibular system becomes a major issue.
Plus, then there's the issue with ensuring that the station remains balanced, and the additional material strength requirements.
I don't think "spinning space stations" is quite as simple a solution.
While traversing between the two parts might be tricky, the craft could be divided into manned and unmanned part connected by cables, to reduce "traffic" between the two to a minimum.
I'm no space engineer, but even I can spot a huge number of problems with going with a cable-counterweight system.
https://www.nasa.gov/image-feature/sept-14-1966-gemini-xi-ar...
"On Sept. 14, 1966, the Gemini XI spacecraft is tethered to an Agena target vehicle. Gemini XI command pilot Charles "Pete" Conrad and pilot Dick Gordon are maneuvering their craft to keep the tether taut between the two. By firing their side thrusters to slowly rotate the combined spacecraft, they were able to use centrifugal force to generate about 0.00015 g of artificial gravity."
Why this is not being used now ? I guess because it was not seen as a priority for Apollo and followup (US) missions as they usually took just two weeks at a maximum. Health effects of microgravity have been also understood in more details & how they can be overcome for the short flight durations.
With the ISS & missions lasting half a year (and longer for some crews) artificial gravity would indeed be more useful, but hard to pull off for a big permanent installation like the ISS, that needs to maneuver to accept spacecraft while also providing reasonable microgravity environment for experiments.
"Microgravity research" is entirely pointless. A total waste of time. It's an excuse to stay on the ISS, that is all. There would have to be a thousand problems solved with fundamental human biology for us to live in microgravity, some of which are at the genetic level. Alternatively, and much more simply, we could use rotating space stations to simulate gravity. That requires just a few dozen engineering problems to be solved, none of which are fundamental. Admitting that the problem was "solved" in the 1960s would remove the excuse to keep sending people to the ISS, cut NASA's budget, and retrench a bunch of bureaucrats. So of course, NASA management is carefully ignoring the simple solution so that they can keep receiving funding for solving the difficult problems.
"Space telescopes" are fantastic! We need more of them! But NASA keeps blowing their budget on the aforementioned waste of time microgravity research they're doing on the ISS instead of the much more scientifically useful telescopes. Many have been cancelled or delayed. Remind me, where's the James Webb space telescope again? Oh yeah... on the ground, that's where.
"Military applications" are not a good thing. "Every gun that is made, every warship launched, every rocket fired signifies, in the final sense, a theft from those who hunger and are not fed, those who are cold and are not clothed."
"Resources in space" is commonly trotted out, but first consider that your argument for the militarisation of space is directly contrary to an argument that space has resources. Military spending, as the quote above by Eisenhower points out, is wasting resources that could have gone towards productive uses. But even ignoring that, the problem with resources in space is the ludicrous cost of moving them to where we want to use them, which is here. Even if, say, we get costs down to $50 per pound of returned raw material, there's only a handful of metals that would make that worth the bother, none of which are abundant (or concentrated!) in sources outside the Earth.
My point is that all of these apologetics for space, or more accurately, for NASA's current approach are false.
We can spin space stations, there's no need for microgravity research.
There's no territory in space worth fighting over. No oil wells in the desert we need to bomb. Space doesn't need to be militarised.
There are no places outside the Earth where liquid water had concentrated minerals into worthwhile deposits. A trillion tons of gold is worthless if it's evenly spread out in a billion-trillion tons of rocky asteroids.
Nobody really wants to live in space. If you think that you do, I challenge you to move to a place much nicer than any place in the solar system for a year, like Bouvet Island. It's a barren island just off the coast of Antarctica. Live there for a year, come back and tell me you like it, or shut up about how it's the inevitable future the human race is yearning for.
PS: Meanwhile, SpaceX is doing all of the truly useful things that we need in space. We need a global satellite-based Internet service that isn't slow and expensive. That's astonishingly useful, right now, and isn't something NASA could ever deliver despite a much higher budget than SpaceX.