Whether or not Emet is a good person is very much a matter of perspective. Which in turn is something that the writers themselves have acknowledged across a number of official interviews. There's also a lot of different reasons as to why he is liked, so it's not as if it can said that his popularity is due to the same reasons across the board.
One thing I will point out that may have been missed by some is that there's an entire scene in Elpis where Hythlodaeus points out to the player character that Emet frequently travels Etheirys and works tirelessly to help those he meets without demanding praise or gratitude for it.