All players are underestimated by some and overestimated by some. It can be connected to flag waving or nostalgia or personal taste, but there will never be any total consensus on who the greatest players are. The GMs at chess24 ranked the top players as 1.Kasparov 2.Carlsen 3.Fischer 4.Lasker 5.Alekhine 6.Karpov 7.Capablanca. I think they underestimated Lasker and Karpov a little, but it’s a reasonable top seven even if most would change the order a bit based on personal preference.
Of course. All people have prejudices and preferences and some even have agendas.
I, personally, find that the focus on the concept of WC drowns out other aspects of the game that to me are far more important. And the concept of WC isn't even necessarily what it seems it should be. The WC may or may not be the strongest player at that time as there's luck and contrivance that often plays as big a role in determining winning or retaining the title. Trying to guess the 'best of all time' using objective means such as computer analysis is pointless because it always favors the later players through no fault of the earlier players and underestimates the sporting aspect of the game. Guessing by using results is equally deficient since the competition is just as different, dependent upon the times. So it's all a game designed to produce arguments rather than conclusions.
I'd rather just appreciate each era and each player for what they contributed to the game (this has been the essence of my writing during the last quarter of a century). At the same time, I value honesty and integrity in examining these things and try, hopefully with a modicum of success, in maintaining those ideals myself.
Fischer's issues were essentially against the governing body of international chess. He 'quit' chess because of politics (both chess politics and general politics) and its interferences in the game.
His talent is beyond doubt.