When I first started smoking cannabis, sometimes I would get so high that I would actually see the world moving signficantly more slowly than normal around me. One time I actually had a complete out-of-body experience occur and returned to reality with the most intense version of this slowing effect I ever experienced, so much so that I wasn't even able to walk properly because I wouldn't see my body move until seconds after feeling myself making the movements, like it was both slowed down and lagging. After about three months of solid dank smoking, I suddenly never experienced this effect from cannabis ever again.
After years of smoking and practicing meditation, I started to get significant closed eye visuals from cannabis while lying in my bed in the dark. This built up over time to the point that one night I had a full-blown dissociative-like experience with a total disconnection from the body and self, cosmic abstract imagery, and total submission to a bathing white light followed by a completely immersive, controllable, and psychedelic dream-like experience. Afterwards, I never experienced this state again and it became difficult for me to get even close, though I do still get tons of hypnagogic imagery very readily from smoking cannabis in the dark.
Aside from these effects, I have not experienced any seemingly permanent tolerance from cannabis, even after years of all day every day use. I also have enjoyed synthetic cannabinoid use from time to time and have never had it permanently alter my highs, though they did build cannabinoid tolerance in general more quickly than cannabis, which required the typical tolerance break to reset, a few days to get back to "normal" or a few weeks to months to make it almost like new for a short while.
Unless maybe someone has completely abused synthetic cannabinoids to hell, I can't imagine a situation where they shouldn't be able to get at least somewhat high; I know several people who have been regular smokers for just shy of half a century and still very much enjoy good cannabis.