not that i'm an expert or anything... but i am more of a lead guitarist than rhythm...
if you ask me, refusing to learn more theory because it stifles creativity is a crock of shiteee, if you'll excuse the expression. it's a bit like saying that learning to spell and learning grammar will make you a worse writer. just because you learn it doesn't mean you have to slavishly use it all the time (if someone asks me to play a mixolydian mode i can do it, but when i'm just noodling, 99% of the time i'm in minor pentatonic, position 1), and also if you don't know more advanced theory, for all you know you're just using that advanced theory without knowing it. i always find it pretty funny when people say they get worse at writing songs when they learn theory- that's not true, they just now realise that they were using over-used cliches and progressions all the time! :lol:
that being said, learning more theory won't necessarily help your soloing, but it shouldn't do any harm either.
play and improvise a lot over backing tracks, songs, etc. etc. learn to play by ear, too- learn what sounds good, regardless of the theory- theory is a suggestion, rather than a rule.
concentrate a lot on vibrato (and by extension, bends etc. and other inflections which make a note sound more interesting)- you CAN practice it, anyone who says you can't is again talking utter cr@p. if your vibrato and bends are good but your chops aren't, it sounds like you're a kickass player but are tastefully holding back (lol, this is what i go for). however, if your chops are kickass but your bending and vibrato aren't too good, you sound like that dude with the shades and crazy wallpaper whose youtube vid was posted in another thread.
most importantly, which lead guitarists do you really like? listen to them. listen to them again. fast forward to the solos. listen really closely. etc. etc.
:)