Most of Mbappe's goals came against weak teams. Two of his goals came against Poland, two against Danmark, and one against Australia. And in the final, although he scored one goal by himself the other two came from penalty kicks. And during the initial 80 minutes his performance was pathetic (although he made up for that in the next 15 minutes of regular play and 30 minutes of extra time). I thought that although he received the golden boot, there was nothing special in his performance this time. For comparison, I would rate Julián Álvarez ahead of him.
Merit of Mbappe in my opinion, it's supposed to be weaker teams, but another players faced weaker teams too and not scored too many goals like him, total merit.
With penalties or not I believe it's his merit.
In final he did a hat trick and it's not easy, the french team played bad during first half, and only after substitutions the team started to play like it's used to.
But I respect your opinion, soccer is funny, look at Di Maria, he didn't do a top performance during the cup, but at the finals he did the best match and helped Argentina. I'm sure Scaloni regret the decision to substitute him after he thought the match was easy.
Yeah, it's a problem with golden boot reward because it is not awarded to the best offensive player, but to a player that scores the most goals during the World Cup. There probably are better offensive players than Mbappe, but rules are rules.
It's not exactly a problem, there's 2 awards in this case:
Golden Boot to the player who score more goals
Golden Ball to the best player of tournament
The only possible way to measure the golden boot is goal