Wow, game seems to have improved decently. I always stopped playing due to bumping into certain bugs or bizarre issues and always gave up, came back 3 months later only to bump on them again. Right now I haven't noticed any major issues, and building a little moon base with a station 3km over it doesn't utterly RIPs my FPS like it did some time ago.
I cannot play without Easy Inventory mod, Twin Grinders/Welders, Nanobot Build and Repair System and Taladen Inventory Manager script if I want to get anything else done on singleplayer without taking my whole week, though.
But even combat with AI ships felt passable. I started a "start from zero" playthrough with only that moon pod buggy, and once a Mining Carriage appeared in orbit I flew there with nothing but my jetpack and a grinder. A couple quickloads later I had a large ship and retrofitted it with Twin Grinders, more engines and more guns. It has 4 Twin Grinders and 4 Landing Gears in front, so I can just grab unsuspecting ships and throw them at a meteor while raining gun fire at them, and later I can grind them down on the spot. Or just disable it, grind it right there, dump the components at base, and repeat.
Twin Grinders is too OP so I keep them off on combat however, but honestly atm I cannot be bothered to build a grinding wall or whatever. I don't know why the idea of grabbing innocent ships, disabling their engines and throwing them at planets on 300m/s+ is so enjoyable to me.
I might try the campaign eventually, but I'm really looking forward to playing with the Exploration Enhancement Mod again, and stealing every design and throwing them into their own stations.
EDIT: After posting this I remembered that completely disabling all engines of a vessel and flying too far from it will despawn it, as unowned/AI objects without control get despawned very quickly (similarly to KSP if I remember correctly). So I guess I gotta keep a single engine on'em when throwing them around.