is it worth doing all the random activities and shit or should I just finish the main quest and uninstall? i've done every faction and upgrading my ship further seems pointless. level 65ish
It's been a while since I played but if you haven't done NG+, you don't have your Starborn ship yet? Every time you finish another NG+ your ship and Starborn suit get upgraded to a maximum of +10 iirc, which is the best armor in the game.
Multiple NG+ are also necessary to collect all the space shouts.
Level 65 is not really that high, but I assume you can already kill level 100 enemies easliy? They appear on the furthest solar systems. I've found the best way to level up is to kill level 100 aliens. Find a spot with a high density of them (usually a coastal tile) and go hunting.
To kill level 100 legendary enemies you'll need a good weapon. I don't remember what the affixes were exactly but there is a "best" weapon for each type. I think it were the Va'ruun weapons. Also armor. You could grind some high level dungeons to farm for better gear. Every dungeon has a boss and a chest, always at the same location.
If you're not playing on the hardest difficulty, I would suggest to do so because you will get more legendary drops.
Basically, if you enjoy grinding you still have much to do, but that's not everyone's cup of tea. Otherwise, if you've done all the quests, I don't think the random activities (I assume you mean the "radiant" bounty hunter quests and shit?) aren't really worth it. But they can add a little variety while hunting for loot/xp. Keep in mind that you will lose your ship and all of your items on NG+, only the Starborn suit and ship will persist and get upgraded. So getting invested on the first "run" isn't advisable if you want to go for a more complete playthrough.