I heard that Blitz can't grab mushrooms anymore.

This only counters a poor blitz. I don't consider myself a great one but there are many tactics good blitz players will use to get around this and I'll list a few.

1.) I get many kills by timing my pull right as the creep your standing behind dies. So if your standing behind a creep make sure he's not getting focused and about to die.

2.) A lot of good blitz players carry clairvoyance. This allows them to get a pull where you can't see them but they can see you. Often I pull people into the forest when they think they are safe at their tower. So I can get you from the side even if your standing in front of an army of creep.

3.) Flash, people assume the only way I'll initiate a gank is through a pull. So there they are sitting behind a wave of creep assuming they are safe. Flashing beyond the creep gets them every time. Then I'll knock them up and when they try to run I'll use my pull.

4.) Baiting is probably the best against an aggressive lane. A blitz with high mana makes great bait because of his passive ability. If the player is too aggressive I'll bait them out from behind their creep wave and then pull. So I'll let myself get low and pushed back to my tower and then start baiting them in front of their creep.

Even some of the best players are suspect to one of these tactics.