If the carpool stickers had come with a 20 year guarantee then nobody could reasonably be upset about the rules changing later because “forever” turned out to be too good to be true. This would be like solar, except that they want to change the rules later anyway.
If they simply left the original EV carpool stickers grandfathered but stopped giving out new ones, people who missed their chance would be upset. But the program would have worked exactly as intended, to incentivize early addition of EVs by giving out a priceless benefit. It should never have gone on as long as it did, but government reacts slowly.