Good characters always help and actually are crucial in making a film work. The story is flawed and doesn't have the imagination or originality of 'Finding Nemo', but the energy, humour and emotion shine through more than brightly and one does relate to Dory in her quest, one that anybody can relate to if in her situation. Humour and pathos are balanced deftly in 'Finding Dory', with the humour hilarious and in abundance and the pathos bringing genuine tears and emotional power.
Where Pixar has always excelled at its best is the balance and execution of humour and pathos. The music score is rousing, whimsical and nuanced. However, the animation is wonderful with an even richer colour palette perhaps than 'Finding Nemo' and matches that film in meticulous detail and visual imagination. The film does meander in places with occasional draggy pacing and a couple of rather too convenient plot devices, and Dory's memory loss shtick does get repetitive quickly that it does grate too early on. While it is not as good as 'Finding Nemo', 'Finding Dory' is a worthy sequel and one of their better efforts since 'Up'. Pixar have been hit and miss since 'Up', with some great films like 'Toy Story 3' and 'Inside Out' (which are two of my favourites from the studio) and some disappointments like 'Cars 2' and 'The Good Dinosaur' (don't hate them as much as many others do though, also didn't think 'Brave' was that bad, though it was not the best animated film that year, and liked 'Monsters University').
'Finding Nemo' to me has always been one of Pixar's best, colourful, imaginative, hilarious and poignant with great characters (who cannot love Bruce the shark, plus Dory speaking whale is one of Pixar's funniest moments).