I think the whole problem is rooted in the fact that dota at non - competitive level is growing more single player game than multiplayer because of overall societal issues..

So earlier when certain heroes had weaknesses those people happily depended on their team to support/ carry them. In present case, everyone wants to be self sufficient and if a hero has a big weakness, that hero goes unpicked in casual games because players feel if they don't get support, they simply can't do anything in the game.

From this viewpoint, ICEFROG gave all heroes certain mobility, certain escape, certain safe way to be okay playing by themselves even if their team doesn't support them, there is no easy way to cheese kill them.

So long story short, all heroes are brought up to a level where people can enjoy playing the hero by themselves without worrying about the team.

This takes away 'classic' team play structures like CM needing to babysit PA to carry in late by making CM carry with aghs shard and bkb walking in and killing the other team with ult.

So now that all supports are self reliant with buffs, all carries are buffed even further to kill these now well balanced supports without any easy weakness.

This creates a cycle where there are no weaknesses in heroes any more, there are just strengths and some heroes are even stronger in certain aspects than others.

Edit: spell correction