Well, Alex Pereira can not please everyone, and even targeting to please anybody at all, but surely even though he is not smiling more often he doesn't really need it, because this is UFC, what is important here is if you can beat the other guy which Alex Pereira is really capable of knocking the other guy out for sure, well he doesn't need to be likable because people does like him the way he was now, even though I am not a fan of Alex Pereira because I am for Israel Adesanya, Pereira surely got the attribute in being a champion,
I have a complete opposite vision. A fighter would better smile, talk, jump and act like an asshole, then be silent but skilled fighter. And the more bad guy you are, the better it is. UFC does not like fighters who are active online inside octagon. Demetrious Johnson is a great example. The guy is so much positive, that UFC exchanged him for other fighter (Mighty Mouse has 11 title defence, lost to triple C and got exchanged for Ben Askren lol). No wonder why people dont love Dariush, Muhammad or Whittaker. Because they are too good as persons 
People dont like Pereira, because he dont speak English, shows no emotions, and got title fight after beating 3 average guys (2 of them were not even in top15), while others wait ages for a title fight. There are actually positives and negatives for both sides. A fighter can jump around and act like he's the best in the world in any circumstance and bring in better revenue for the fighting organization or company and at the same time bring better money for himself as well.
But that also comes with consequences. Remember in the past when Muhammad Ali did things like these and got millions of death threats?
It's not like he was not loved by the people. But there were a lot of people, even the mafia, trying to kill him. But at the same time keeping quiet and just being the best is probably not going to bring the most amount of money. About it does increase respect.