TBH if some of the criticism was actually legit I think people would take it more seriously. Saying "Oh it sounds just like Kesha, it sounds like Katy Perry" does nothing b/c IMO it doesn't sound like them at all. Britney worked with these guys long before those girls ever did, and was experimenting in electronica and heavy-synth wayyyyyyyyyyy before those girls ever picked up a mic (or became well known). This is Britney and her team further exploring dance music and infusing some other genres into it.
As a Britney fan I admit it's not revolutionary, but as I said earlier, it's the quintessential Britney song that is playing not only to her fan base, but also to those who maybe wouldn't have given her a chance before. HIAM is MUCH better than Womanizer, better than most of what was on Circus. Instead of giving us Blackout 2.0 (which might make some happy), Britney is continuing to look forward, not repeating herself or trying to be someone that she's not.
Musically, “Hold It Against Me” sounds a lot like what Britney was doing on her 2007 gem Blackout, perhaps the most influential pop album of the past five years
It’s funny how people underrate Brit’s impact on the way music sounds now, just because her personality gets in the way, but if you listen to an hour of pop radio today, you’ll hear an hour of people trying to top Blackout..