My kids wear masks to school too. My oldest is probably not as heavily impacted by this but I feel like my younger child has been (started K in 2019). He doesn't really know what his friends look like, he doesn't get to see facial expressions of his teachers or peers as part of their emotions, he doesn't get to see the teacher enunciate words with their mouth, he's spent a lot of time learning virtually at a young age, he gets to hide his own reactions behind a mask. He's soft spoken and his participation in class is probably suppressed a little further and dampening him being challenged or as confident. Compared to my older child, there's less enriching extracurricular activities available for the last two years as well, clubs and PTA events and sports have all been impacted.
I have no way of quantifying any of this but there's just tons of little things that have the potential to be negative impacts to his long term success. Even if my kids cope, I worry about their peers and the worrying trends in academic test data compared to previous cohorts.