This discussion has been had many a time. However I guess I can just say it again. The problem is, many high level pvp teams require at least ONE form of def wall. Be it spdef or just def in order to wall common offensive types. This is a hard counter to help setup sweeps etc. The issue with Shadow tag is, in the form of a Goth, is that if you try to wall a specifc poke, they can simply swap in Goth and boom goes your ability to defend against sweeps effectively.
So now you're left with either tech pokes or just general sweepers that will come against THEIR walls and you don't have any particular means of getting rid of it in a timely manner. Goth doesn't JUST rek full stall teams, it reks any team that dares to have a non physical attacker/ or a wall IN play.
Nobody is arguing that you can't kill a Goth, its easy to kill, its that there is no COUNTERPLAY prior to it being revealed from your opponent's lineup.
Its so easy to play vs gothitelle really
if you wanna run sp atk sweeper, make sure you have volt switch on it, or TAUNT
taunt reks gothitelle, especially taunt hydreigon. There are always solutions, just people dont wanna ruin their perfect stall teams.