I just finished watching TMP (I’d seen parts of it before, but not all the way though) ...Kirk and Spock’s interactions really don’t make sense unless you assume they’d had a messy/awkward breakup some point before Spock returned to Vulcan
Some somewhat spoilery thoughts on TMP and Beyond below:
In a sense, Beyond is a crossroads of sorts- particularly regarding Kirk and Spock’s decisions about where their futures lie.
It (to me) seems to be the AOS’ version of the (unseen) decisions that TOS Kirk and Spock made to accept promotions and return to Vulcan, respectively? I mean, the parallels aren’t exact (it’s partway through the five year mission and AOS’ Spock does not seem to be considering undergoing Kolinahr) but still...
On a less related note, I just realized that TMP and Alien were released in the same year. It's interesting how different the two films look (and how much more... real Alien's costumes seem)