I eat out a lot and the shrinkflation I have been seeing, in all restaurants since covid hit, is simply redonkulous. It's the most constant topic of conversation at our mealtimes, which items we discover that very day that have fewer items or smaller portions for the same price. It's absolutely constant now.
I haven't touched a big mac in years, but if they are even 50% of the size that they used to be I can guarantee you that most of their weight is strictly cheap additives somehow. Probably cancer-causing additives, too. They just stopped caring last year.