Ok.....I have to ask!

Back in the day, lefty pitching was thought to be a rarity and teams were fortunate to have one good one. To have two was unheard of. Also back then a lefty could throw 4-5 mph slower than a righty and still get a good look when they would not even consider the righty.
Today it seems to me that there are just as many guys who throw from the wrong side as do from the right. Yet I still read and hear that lefty's can get a good look even if they throw somewhat slower than his counterpart. Is this true or has the advantage of being a lefty disappeared.