Obviously this is all down to opinions and what you define as 'greatness' in a player. I wouldn't say Mahrez is the greatest player ever to pull on a Leicester City shirt. I would put many of the players in the early sixties and those of the Bloomfield era way above him on all-round effectiveness. He has skill, that can't be denied. But skill alone doesn't (in my estimation) define greatness. You need much more, not least application and effort. Football these days is far less physical than it was in the sixties with players now being given so much protection. That is no bad thing because everyone likes to see skill, but it is still a physical game and Mahrez struggles in that area. Wellernever - I wonder if Mahrez would have done many incredible things if Ron Harris had put him into row Z with his first challenge of the match.
Football is a team game with the team being made up of players with many different attributes. Against some opposition you can afford one team member to go missing defensively. But when things aren't going so well, as in the first two games this season, we need everyone to show their togetherness and team spirit, to get stuck in, make things happen and turn the game around. Those are the things that team mates and good players do for each other ..... and Mahrez isn't doing them. And yes, for £100k per week (which indicates he is considered the best player in our team), putting in the effort should be a given.
So no, I can't accept Mahrez is an enigma who should be forgiven for not giving his all. The fact that he has won a Premier League title doesn't make him a great player. It's the team that wins the title not an individual. There are many average players who have won title medals and there will be many great players who don't.