That’s true. But it’s also true that players have always been recruited over by incoming frosh and JUCOs, and that the way those players get playing time is to go to a lesser school (which is also now easier). And there will be players on some schools that get playing time because players in front of them head to greener pastures who wouldn’t have before the portal.
Ultimately, the same number of young men will be college starters and college rotation players with or without a portal. Some will benefit from the new ease of moving, some won’t.