You're not missing much with BoS to be honest. I find the came very frustrating and the controls play against you way too much. Tactics seems like the better option spin off, I've not played much of it but I have about 3 copies of it (It's a long story) so I should play it soon. As for an antagonist, I'll disagree, 1&2 had a clear antagonist in each of them, but it was more on how you dealt with them that mattered.
I didn't feel that. The Master was really not a huge thing until the end game, and by then I was more curious about him than anything. You could also join him for a really sick end scene, which made me feel evil (and that evilness had a purpose, just like the Unity did.)
Desperation. Though with how badly optimised it is for modern systems and what you need to do in order to get it to run, I'd rather not. Only way I think I could ever play it is via the TTW mod (and that's only by accidentally accessing 3's content rather than being on purpose).
Fallout tactics, a game made by an Australian subcontractor that mostly make cell phone games today, that had less time of development than initially agreed, that shows a better understanding of the lore than the multi-billions company that actually bought the IP, has the best combat system of the whole series ( and environment interactions), has more endings than fallout 3, despite not being an rpg and not being marketed as an rpg, nor as a sequel. (And your character build actually matters) It doesn't compete with fo1, fo2 or fonv, not that it was even intended to, but it is much better than fo3, fo4, shelter or bos.
It has more endings than Fallout 4, given that 3/4 of the endings to 4 gave the exact same ending clip.
To remind how bad fo3 was? I'm currently replaying Fallout 1,2 and NV and I think I'll replay fo3 to remind how bad it was.