The difference is that before you walked up and got in line or got in early enough that you walk in and choose your seats. And your position was based on your arrival order. Now, you walk up and sorry all seats but the front were bought up and no they aren’t here yet of course. Why would they be? It used to be you just timed it so you got there 30/45 minutes before the start.
I’m just yelling at clouds honestly. It’s not that big a thing, and I reserve seats nowadays often, but mostly because I basically have to. Also, theaters are only ever crowded enough to care during tent pole releases and nowadays I just wait a few weekends.
I just find the social contact of getting to the venue when an event takes place early/on time to get your pick a better experience than choosing a seat on an app early. Probably a condition from growing up pre reservations.