The problem is not with sitting in high chairs ever, at any age. The problem is with being carted from one stationary place to another and never getting to move about, even up through age 3 or 4.
My kid eats at least half his meals standing on his feet, starting when he was 14 or 15 months old, either on the kitchen floor with a low table, or on chairs at restaurants. Another quarter of meals he is sitting in a high chair. The last quarter he is sitting on someone’s lap or a booster seat or some other arrangement.
But someone could certainly sit in a constrained chair for every meal up through age 2 and still manage to get plenty of time to move independently. From age 2.5 or 3 kids could be sitting on a Tripp Trapp chair or the like, something that lets them sit at the table without being stuck.
Eating soft and pre-processed food is similar: kids who don’t have any molars yet can’t chew much, but I see 3-year-olds eating nothing but mushed up food. Biting and chewing hard foods is what the jaws and teeth were evolved to do, and if they don’t get a chance they don’t develop properly. I had friends whose parents cut the crust off their bread, shelled nuts for them, peeled shrimps, only ever gave them boneless pieces of meat, etc. even as teenagers; we shouldn’t be infantilizing people who aren’t infants.