I agree that in the context of the story (unless something is way over my head) Sulu’s sexuality wasn’t ever an integral part of the plot - but I’d still question why there is any point in changing it - and to me, the answer (based on the information I’ve read) is twofold: firstly to honour an actor who does not want to be honoured in this way and secondly, to help normalise gay marriage.
To me, even though ST has always presented a very inclusive and diverse vision of the future (albeit one where all the aliens have done the decent thing and learned to speak fluent American English even if they do wish to destroy all humankind

) including pushing the boundaries with the first televised interracial kiss, re-packaging a character as gay in this way still sits uncomfortably with me because it doesn’t appear to have been done in order to bring something extra to the story and it’s drawing attention to an actor, rather than a character, which goes against what all the actors I know are trying to achieve.

I’ll shut up now, because I think I’m in the minority with this view!