Offsides is the most fundamental part of soccer, IMO. Without it, the game would be completely different. I like that the defense can strategically condense the playing field with the rule (playing a high line), thus forcing offenses to adapt.
The lack of timeouts/commercials is fantastic.
Relegation leagues are awesome. I like that regular season greatness is held in a higher regard than tournament-style championships (although the Champion's League is probably challenging that assertion).
I like that when there is a dead-ball event, the game can sometimes just start up again without all of the exactness of American sports. Same thing with 90 minutes. You just keep playing until the ref says the game is over. It's like the game just isn't taken so seriously... With this said, VAR (video assisted referee) has been horrible to this effect. Who cares if the player was an inch offside, let them play!
I don't love penalty kicks, as they seem to disproportionately penalize the offending team for certain fouls in the box. But I also don't always love the way free throws in basketball, either.
Flopping doesn't bother me at all in either basketball or soccer, but only because it's the only way to get refs to call the foul. If basketball players didn't flop, there would never be an offensive foul called, and if the most talented players in soccer didn't go down easy every now and then, they'd just keep getting kicked over and over without the ref calling the foul.
In many ways, I like soccer because it hasn't been so Americanized. It just feels different.