I've been playing Pokemon for nearly 15 years and am only JUST now learning about competitive strategy (acckkk). I learned about EVs during Gen 4 and tried training (I'm assuming) a Dratini but got lazy and gave up. I fully EV trained a Dragonite about a year ago on Black 2, but its move set was terrible and the IVs sub-par. I knew about IVs by then, but went with "good enough." I think it was a week or two ago that I learned perfect or near-perfect is not at all unheard of and I'm currently trying my hand at. . . not being an idiot. In the mean time, though. . .
Strategy up until recently has been all-out attack. I wasn't afraid to use status ailments, but anything that helped stats received an automatic "no" from me. I'm inclined to blame the god-awful AI and wild Pokemon constantly using Defense Curl even while I hit them with special attacks. AI doesn't get smart until post-game and I've largely been a play-through type player. For the longest time, the only things I understood were STAB and type effectiveness. Physical vs special, nope. Didn't learn until they switched. Status boosting moves? Literally a week or two ago. Even my Hall of Fame X file has a Raichu with four electric attacks. I at least don't use one OP Pokemon for everything - I learned my lesson after my first Blue playthrough. 80-something Blastoise never stood a chance. I didn't even bring any elixers. I struggled my way through Lance and then the rival killed me.
This has been a long response. Basically, I think I covered every flaw that everyone here has said. I've done it all. I'm a noob who's been playing for 15 years.