Ironically that's because they are more solid. The new lines use a harder plastic, that allows for better details but makes them break to easily. The softer plastic of the old WotC minis couldn't hold the same details, but was absurdly irrepressible. No matter how you mistreated them, they would bend, but almost never break.
I miss those too, they were so much easier to transport. Just haphazardly toss them in your bag, let them be thrown around and curshed by the heavy books of bottles also in the bag and still be sure that they come out intact. Sure the formaly straight spear and longswords look like hooks or sickles afterward, but they're still attached
However the pathfinder minis do have a much better average paint job quality than the WotC sets. The WotC sets had their highs and lows, and while the highs certainly beat the pathfinder minis, there were so many low quality paint jobs that the average of the pathfinder minis is superior