The technical regulations for each season are published well in advance and it's up to the teams to design a car that will go as fast as possible within those regulations. They all knew that the tyres would be getting even more marginal, Pirelli made that very clear. If some teams balls it up and build cars that are slow, that's their problem.
Pirelli have announced that they're going to revert to last year's tyre construction to make them more durable and I'd question how ethical (and legal, for that matter) it is to just suddenly change the regulations in the middle of the season because some teams have discovered that some other teams have done a better job designing their cars than they have
Now I agree that changing the tyres is necessary, but for next season, not now. Changing them now isn't much different from saying, "oh, McLaren and Mercedes have designed cars that lack downforce this season, let's ban front and rear wings for the rest of the season".