Jasper was a pretty weak villain tbh. Every other enemy encountered thus far has had some another side to them (the monsters are corrupted gems, lapis wanted to go home, peridot wants to study the cluster). Jasper just cares about strength. I mean, she's practically vegeta.
I personally wouldn't call her a weak villain at all.
She was really engaging to a lot of viewers, and trust me thats a big win in storytelling (I hope I could create a villain as "weak" as her).
Jasper really didn't need to have a back story and character development on the level of the crystal gems or even some of the corrupted monster gems to be an incredibly likable, and entertaining character.
Hell, she is much more interesting to me than any of the monsters we've seen so far.
Like, I love the design of the monsters and the fights that surround them...but they're just moving MacGuffins most of the time...barring the centipeedtle and maybe the lighthouse gem, they don't tend to show a lot of feeling or have noticeable back stories beyond being corrupted gems; they roar and attack the good guys to get the plot and story moving.
Jasper as a character had agency, vices (her hypocritical stance on fusions, her unreasonable temper, her fusion prejudice, etc.), values (the homeworld, tactical skill, strength, etc.), and a focused purpose.
I mean...valuing strength is no more shallow a value than wanting to go home or wanting to do your job; it's possible to create some really engaging stories from a character who mainly values strength, and that's what the crewniverse did.
I mean, it makes sense that she values strength tbqh; going by her "...looks like another waste of my time." line it seems like she might be the exterminator non-action gems like Peridot call to take care of bothersome infestations so they can get back to work, if this is the case this line sort of tells us that she hasn't been truly engaged yet and her job is mundane at this point.
Edit: Generally going by my own storytelling experience...a weak villain is just an unlikable/"charmless" character with unbelievable motivations who is just doing stuff just...because.