I think it's common for people to jump the gun and attack simple logos out of spite. Most probably assume the logo was easy to come up with when in reality the simple ones are the hardest. Humans tend to forget that less is more and always assume what others want without doing enough research to validate the assumption.

The end result, in this case in particular, is simple not doubt, but the problem with logo design in general is public perception of value.

Simple logos may have very well come together quick, but what you don't see is likely the massive amount of iterations, concepts, brainstorming sessions, sketches and more that went into creating it. This part of any design process doesn't get advertised and is why you have apps like Fiverr or something who offer logos for $5.

Just my $0.02 but you get what you pay for, I think the rebrand is solid and iconic. Mastercard needed to evolve. Pentagram helped them with that. The fact Pentagram worked with Mastercard automatically promotes value in their new logo mark for those who know of Pentagram and their long time success with brand development.