If you never use them what is the point in keeping them?
For meta changes, really.
I never used fusions or linear fusions until this season, and randomly keep a few of them did pay off in that I didn't have to grind for a Cartesian or a LFR this season.
If you need the vault space, toss the least appealing ones.
That's the problem with the grinding in the game - you can't easily infinitely grind high level content for the perfect god roll, so you end up with many versions of slightly different variations of the same thing.
Even with the same primary perks, I have Fatebringers with max range and max stability and it's like... which one makes more sense? That's before you get into PVP and PVE versions, which admittedly is less a concern for me but I still few compelled to keep PVP rolls for some reason (opening shot being a thing apparently).
It's a question of marginal differences for sure, and if raid and GM weapons were easy to come by, it wouldn't really matter to me which is why I'm happy to shard Gridskippers and stuff (although now that those are going away, I feel the need to keep some of them too).
I like the adept one for anti-barrier duty despite hating 450s in general. If you like it, keep it.
I have several of these as well, but I wasn't able to get the One For All/Overflow roll I wanted on the adept version, so gotta keep that one too... and then it's like DIM says keep another one that has Killing Wind/Disruption Break for PVP.
For stuff like that you can post the rolls in question. People will be happy to provide recommendations. Sometimes all that is needed is an objective pair of eyes that know the game well enough to help adjudicate.
As a baseline everything is "DIM approved" for me, then it's specific perk rolls that are either equally good or "differently" good that it just becomes indecision for me.
It's hard to nuke Timelost weapons because they're relatively hard to get, even though I've definitely killed a lot of Visions, Fatebringers and Praediths out of necessity. Then the GM weapons, seasonal weapons, and basically other stuff that isn't easy to get.
If getting a Timelost drop meant it entered the general world pool and you could have a chance to get it from other activities, then it'd be much easier for me to just let go like I do with all the generic Banshee/Rahool/Vanguard/Crucible/Gambit drops that you are constantly fed.