Player count isn't the only factor and deciding if something is fun or not in BF. But it is though one of the key contributors to how a certain map and game mode on that map is playing out.
Just above some remarks were made around old classic maps like Locker, Metro, Hainan Resort and Lancang Dam. Personally I have tried playing on all of them many times. Sometimes the gameplay is great structured and potentially even linear in its flow. While other times it could be complete chaos and anarchy.
Some players here in the forum probably prefer one of these but not the other. And there are no rights or wrong here. But for sure the player count is a very important factor in all of it. All of you that have played on maps like Shanghai or especially smaller CQC maps like Locker or Metro knows how that same game mode, e.g. Conquest is changing very very dramatically depending on if you run a server full of 64 players. And the distinct differences then on what kind of play-style will win the match if the player count is reduced ever so slightly to just 50-54 players. And again if the count is reduced further down to just 24-28 players in total. So same map, same game mode. But very very different gameplay and strategies and even soldier loadouts and weapon choices then as result. The game play experience for the gamer is substantially different between playing on these!
One thing is however clear, and now highlighted in BF2042 on some of the maps there when having 128 players on board. Each map and game mode has a certain player count saturation threshold. Upon when reached or adding more players on, then it is always chaos and total anarchy on the battlefield. Hence no alternative experiences are ever to be had on such server if the full saturation is reached all the time.
In previous BF games, what made it fun to come back again for one more gaming again and again was that this saturation point was not reached, and the gameplay would be different from time and again. And yes of course, the individual players making up the full player population on the server at a given point of time have a big influence on how the gameplay then will play it.
But there are limits to how many rats you can put into the same little cage for them still to have sufficient individual space to communicate and thrive without biting each other nonstop...
And my personal opinion is that the BF2042 maps are simply too poorly designed and lack the rich contents between capture zones (that we are used to from prior BF games) to enable meaningful 128-player matches apart from total chaos and anarchy despite their large geographic sizes.