I uninstalled after I got most of the artifact pieces and powers, first pass through. Just played the "good" (as opposed to criminal) storylines, never beat the main story. Am planning on waiting a year or so for mods or major DLC to give it another go.

I enjoyed it, but have played it a lot less then Fallout 4, and I don't really feel all that interested in doing multiple vanilla playthroughs, unlike Fallout 4.

One of the things that The Outer Worlds fell flat on for me was the perk system. There aren't really any terribly-exciting perks there that significantly affect gameplay.

That's not true of Starfield...but it is more true than for Fallout 4, and it really limited my desire to do multiple vanilla playthroughs. In Fallout 4 (and Fallout 76, though there one can respec), I had to make some tradeoffs that forced me into one of a set of playstyles. In Starfield, the combat is far easier -- I never bothered to get any combat perks other than two levels of Ballistic. The only place I ever seriously had to consider backing out and getting more supplies was the Mantis run, and I virtually never had a character get killed, even by the most-built-up major fights. That meant that there was no need to make tradeoffs in choosing perks -- I had a surplus of skill points. I didn't need to play, say, a stealthy character because I could just walk into an encounter, easily kill everything without combat skills, and continue on.

On top of most enemies just not being that tough, as with Fallout 76, most melee enemies are rendered trivial by obtaining a jetpack, because one can normally reach places that they cannot. In Starfield, one can get a boostpack early, and the maps virtually never have open plains without something to get on top of.

So playing through again to play a different spec didn't have much point. My character could already do everything I wanted.

The quests are more-or-less on rails, so there's not much reason to replay them, as one rarely can get significantly different outcomes.

One could do a "criminal" playthrough, but I didn't really want to take that route. Didn't really like playing as a raider in Fallout 4: Nuka World, didn't really want to play Crimson Fleet or gangs in Starfield. And even if one wanted to do so, that doesn't mandate a new playthrough.

Neither the ship-building nor outpost-building aspects of the game require multiple playthroughs, as there aren't meaningful decisions with tradeoffs to make. If anything, they discourage it. And there's not any real "point" to the ship-building or outpost-building other than maybe making a particular aesthetic one likes. Resource production is only really required to, well, build more outposts. One doesn't optimize outpost layout for base defense against attacks or to maximize production or whatever.