DotA is widely regarded as one of the worst made maps in history. Its internal code is so poor that it is extremely prone to bugs, and Blizzard has had to release some 'DotA' only fixes just to make it work. The map size is also ridiculously big, and makes a lot of mappers wonder what in god's name Ice put in it to make it so massive.
In mapping circles IceFrog is also known as a massive tool, because he reaps in fame and recognition for a map that he didn't even make. He is at best a janitor keeping the map clean.
DotA was really badly thought out, a cheap clone of AoS. Where AoS promoted team work and finesse, DotA encourages solo play, and kill stealing.
This map only became popular by having a massive botnet (not sure who it was funded by). And it has been proven that you can quickly and easily get a map as popular using the same tactic.
Besides that, there was an even better AoS, Tides of Blood, which came before DotA. It was a marvel of coding and art, now that is definitely worth a play. ToB was once bigger than DotA is now, but then the guys who made it became inactive, and so it died.
DotA? No thanks.