Yes—Paul seemed to consider chess a hobby at most—a brief dabbling with the game as a challenge to himself, just to see how well he could do with it.
His true passion (and the majority of his time) was devoted to studying law.
Chess eventually became a source of disdain for him. People kept pressing him about it, despite his obvious desire to no longer be associated with chess, and to pursue other things.
Back then, being a chess player was neither profitable, nor respectable. His reputation of being a world-class player followed him around. Plagued him, even. And he grew to hate it. Much to our loss. :(
Steinitz didn't do as well against common opponents with Morphy, and he got destroyed by Lasker. And didn't he also have an overall minus against Tarrasch who was busy being a physician?
Lasker didn't defend his title for long periods of time and got destroyed by Capa.
Capablanca as number 1 can be challenged by his loss to Alekhine.
Alekhine can be challenged by his loss to Euwe and his ducking Capablanca for a rematch.
Botvinnik had nearly even records in WC wins Bronstein, Smyslov, and Tal, and he had the benefit of the Soviet collusions against Reshevsky and Fischer.
Fisher as number 1 can be challenged by his refusal to defend his title.
Kasparov as number 1 can be challenged by his loss to Kramnik, and that he barely eked out victory (though in 3 matches nonetheless, amazingly so) against Karpov, who himself struggled in one of his WC matches against an older Korchnoi.
Morphy, though, has fewer of these direct challenges to his dominance ... People cannot challenge his chess accomplishments directly, they can only challenge the quality of the masters that he hardly tried against. The other thing about the other champions is that, with the exception of maybe Capa, none of them just suddenly burst onto the scene and dominated in such a manner.
I agree that a freshly time-transported unbooked up Morphy may struggle early in an all-time match-up, but genius is genius... Everyone in the mid-19th century had whatever similar resources they had, but Morphy dominated without even the tools those players of the mid-19th century had, namely a stream of the strongest players to play regularly (being in the US instead of Europe). I agree with Bronstein and Fischer, that it wouldn't take much for Morphy to catch up to modern GM's and then I go a step-further to say Morphy would surpass them ... I understand the last part is an opinion, but that is what this whole thread is, arguing over opinions.
I also think it is unfair that these greats are being compared to computers ... The romantics liked to gambit and it was considers unmanly to back down. They could calculate variations as well as modern day GM's. If you destroy your opponents so easily, you don't play your best or most accurate/computer-like. If you are up 5-0 in football (soccer in US), you might decide to rest your star players for the last 20 minutes of the game so they can be refreshed for the World Cup, rather than run up the score to 6 or 7 goals to further prove your team's greatness. Or if your team is already advancing, you might rest your star players in a game that doesn't affect the outcome. It would be unfair for future generations to say "oh they only won 5-1, but the other team 50 years later (who kept their star players in to break a record) beat a more modern better team 6-0, so they are better."
And as far as the advantage of modern knowledge... There are 1800 players who know more about openings, pawn structures, and modern advances than Morphy, but none would come close to beating Morphy. Modern advances are knowledge-based, not logic/computational-based.