I think he ended up both underrated and overlooked rather quickly after the peak of his career was gone, but at the time he was at his best he did have spells as the best player in the world. Probably the most key contributor to Brazil making 2 WC finals in a row, above even R9 who I think was a more unique player, but Rivaldo was more effective in those tournaments.
That said, I looked into why he might not have that much of a media profile and I figured + remembered a few things. He didn't like speaking to the media and still doesn't very much, but that does not mean that he was a quiet and easygoing type within a dressing room. Rivaldo got on well with most of his Brazil teammates but he could be hard to deal with from a coaching perspective.
He was a bit preoccupied with his own image and did have an ego. He threatened to leave the Brazil camp twice, once at the Copa America 99 when the manager played a practical joke on him by saying he wouldn't be starting the first match, and again similarly at the 2002 World Cup when he was recovering from injury and in the weeks ahead of the tournament in friendlies he still hadn't been started in any of the matches. These stories I got from an interview with Rivaldo himself about a year ago with ESPN Brasil. I also remember stores about him complaining that other players were feeding the striker more than him, and that therefore the striker (I think it was Romario in that instance) was getting all the goals and all the plaudits. So not the easiest guy to deal with.
