He is poorly written for reasons that Coby explained better than me. So I would recommend you read their post, which shouldn't be too far back since this thread moves so slow now.
Meerus being magically strong isn't an issue since Whis is also magically strong, but he's a great, well-rounded character because there is more to him than just his power or even his knowledge. He is generally likable, a complete troll to almost everyone especially Beerus, does have a set a morals despite claiming to be neutral in all things, and have quirks like his love for good food. Meerus on the other hand has nothing going for him as a character other than his power and him being good at his job, and seems to exist to show why everyone else sucks compared to him.
The best way to describe it for me is that Meerus feels like he was written with a power set in mind and his job with little to no thought put into his character. While Whis feels like he was a character first, and then they added to his power set. For the lack of better words, Meerus is presented as special without anything else going for his character, which is a common pitfall in fanfic writing.