They're not good enough. It was always the argument. Their core for core performance was just too lacklustre.
Even today, they're still weak.
Which is why I gladly hated on them, but I was more than happy to go Ryzen.
8 Bulldozer cores roughly equal 4 Zen cores.
Which is not a problem. The problem is the poor optimisation of many applications for multi-threading and the spread myth that a dual-core Pentium or i3 is better. Which is nonsense.