He's not entirely the problem now - I think it's a three-tier problem with problems above Gats, with Gats, and below him.
Gatland himself should never have come back - if he didn't, he'd have had a statue on St Mary's Street by now. He did come back though, and by that point the world had moved on from Gatlandball. Other teams could see through it; refs were wise to the cheeky tricks: and commentators could read set plays before the ball had even come out.
The Wales team isn't exactly stellar either. It's a team full of great players, but very few world class players. It's a team that would be sent on tour to the US or to the South Africa provinces five or ten years ago, but not a team that can stand up to top tier rugby.
From above, the WRU have let it stagnate. Cutting development programs and academies; and letting the four Pro12 teams (or whatever it is these days) flounder have given the team nothing to play with for the next five or ten years.
It's an absolute disaster, but I suppose it's given the Western Mail front pages for a while.