DotA had been a very unfriendly game to melee heroes. I suppose in some ways, it's a common trait that is consistent with a lot of old games. Playing melee units effectively in many old games were tough. I mean, it's a simple enough concept; gun controls more space than say, a knife would.
But just because that's how it is in real life mean that's the way it should be in a video game. As the art of game design matured, a lot of fantastic concepts have been introduced that bridges the gap between melee and ranged (the charge mechanic comes into mind). I'd view this as sort of a progression as a whole in game design. Game design moving forward to make things more...awesome.
Well, DotA is rather an old game. But it's also a game that has always been constantly evolving. Back many years ago, the innate advantage a ranged hero had over a melee hero was massive. I mean so big, that matchups were as simple as [ranged > melee]. As ridiculous as it sounds, that's truly how it was. It was very common to see 4 ranged heroes and 1 melee hero in competitive scene. And that was the standard. At most, you'd have 2 melee heroes.
There were no Poor Man's Shield back then, nor was there a Quelling Blade. Vanguard had existed, but it was just as effective on ranged heroes as it was on melee (before it got nerfed on ranged). Not only that, Vanguard is a rather costly item. It wasn't going to help you for the first 10-12min of the game.
But times have passed. Poor Man's Shield and Quelling Blade had been introduced, as well as not-so-melee heroes like Kunkka and Clockwerk. They also reworked heroes like Phantom Assassin so she has a spammable ability to farm with from afar. Then there are heroes like Bloodseeker who brushes off harass like no problem.
So what does this mean? Well, it's obvious that more heroes are viable than ever before. Does this mean ranged heroes are weaker? No. They're still good, but melee heroes' effectiveness got stronger. This doesn't mean that ranged heroes suddenly suck because of it. But what it does mean is that there's more emphasis on matchup knowledge in today's times.
Not to say it wasn't important before, it was. But perhaps, not as much? Because now, you need to know what beats Pudge middle. Or what beats Bloodseeker middle. You can't just send a Mirana (PotM) middle and expect her to keep them down. Because she won't. If this was 2007, she would. But times have certainly changed and now, and as an aspiring DotA player, one has a need to know these things; what beats what.
However, with the subject of counterpicks and general matchup discussion, it also brings up an interesting question: At what point does counterpick lose its effectiveness? To counterpick for the sole sake of counterpicking is probably not a good idea, especially in tournament or scrim settings. Your expertise with the hero matters. And frankly, the opponents' expertise with their heroes as well. It's all relative. Theoretically speaking, strictly from a game theory perspective, the best player in DotA can play every character at an equal, high level. So this question is not a problem. But to the rest of us lesser beings, this is still something to consider.
Though there's much more to discuss of this subject matter, I think I will leave it here for now.