The Empire Strikes Back received mixed reviews initially when it was released. Over time it’s now regarded as one of the better entries of the saga. I think it will be the same with The Last Jedi.
It already is regarded as one of the better entries in the saga. Metacritic has it as 85% positive from critics…
http://www.metacritic.com/movie/star-wars-episode-viii---the-last-jedi
I think its also a fair point that ‘time’ may allow opinions to shift, particularly as it is a middle film of a yet unfinished trilogy. The weird ‘Mary Sue’ reactionary stuff that Adywan just alluded to will also hopefully become a relic of the past, and let us hope that in ten years from now people will be more accepting of diversity and female leads.