I think this shows how subjective all these attempts at finding out when Pixar was good and then stopped being good really are.
Inside Out was a critical and box office hit, Luca was the most-streamed movie of 2021, and Coco was both a critical and box office hit and has seemed to have its appeal grow over the years based on the fact in 2021 it was the only 'older' Disney/Pixar film to make the top 15 streaming list alongside Moana and Frozen. So, while Pixar may have lost some or a lot of those who grew up with their original run of films, they do seem to be building a new audience which is probably exactly what they need to do.
Perhaps part of the problem with Lightyear is that the marketing was pitched more at the demographic who would have seen the original 1995 film in theatres? I mean, is David Bowie really bigger with the younger audiences? Not sure, but I agree with
@TrainsOfDisney that the marketing of Turning Red was certainly a lot more colourful and appealing for a younger demographic. It may seem obvious, but I think Domee Shi's idea of putting red pandas at the center of the film because they are a big, fluffy, and cute way to talk about things that are otherwise awkward was a good one.