Against the Pokemon of trainers who are presented as competent in battling, rarely, if ever, do we see their main Pokemon effectively get one-shot from one super-effective attack. The fact that Skitty was able to do it to a competent Pokemon commanded by a competent trainer is mind-numbing.
What made Erika so competent? She didn't seem all that strong to me. A Jynx is engulfed in Fire Spin and finished off with a physical attack.
You've been watching this show for years, virtually 90% of the shows battles play out with the protagonist beating their opponent in only one or two attacks.