Not to disagree (but I'm about to), but looking at Rotten Tomatoes for DS1 and DS2, the audience score is 86% and 85% respectively. Not to say that Rotten Tomatoes or it's reviews (critic or audience) are the ultimately authority.
However looking at the actual ultimate authority, box office (also not the actual ultimate authority), both films did excellent. DS2 actually technically did better, but that's open for discussion. Suffice to say both did well.
I know there is a lot of distaste for the multiverse online, but looking at the numbers I think it's fine for them to dig in as part of one last ride. (I'm assuming this film is released before Avengers: Secret Wars.)