Of course you're not sure where that mentality comes from. Because you, much like 90% of the people on the Boards who complain about X champion, have absolutely no concept of counterplay or champion balance, and thus think your personal experience is reliable in determining a champion's effectiveness, when this couldn't be further from the truth.
Notice how much Blitzcrank is played in competitive and high elo? Not a whole lot. Know why? Lack of consistency and zero lane presence once the hook is down, as well as teamfight presence.
A champion with one skillshot that can instantly a turn a match into a 4v5? Since when? Ezreal can Arcane Shift during the pull to negate it completely. Mashing Flash after you are pulled by an inexperience Blitzcrank (or pre-6 Blitzcrank) will result in getting away prior to the knockup. Sivir can spellshield the grab, Morgana can spellshield the grab, many champions have mobility like Vayne to dodge it, and many champions even when pulled can very easily get away (Corki Valkyrie, support Thresh pulls ADC in, ADC Kalista pulls support in, etc.). And that's just the bottom lane champons.