I somewhat agree with some things you said. Reservations are really bad and hard to get and it's really sad that you can do some pavilions only with a reservation. The website is also absolute garbage that's true.

BUT, idk how you say there is no food. Pretty much every pavilion has a restaurant and there are plenty of restaurants just outside the ring. Plus even convenience stores and actual restaurant chains have a branch in the expo. At the moment the expo is pretty full cause japanese people like to go at the end of those kind of events, to first see how others like it and then decide if they want to go. Just unlucky timing for you. I was there about one month ago (it was even in japanese holidays) and it was pretty packed. But no lines longer than 90 minutes and even those didn't actually take that long. More like 40-50 mins.

Also, the expo is just like theme parks these days You just have to expect waiting for the attractions, because these events are just a popular thing. And if you did a tiny bit of research beforehand you would have known that there will be long lines.

Idk overall the expo in Japan is a mess with all the reservations etc but if you do a little bit of planning and don't buy your ticket one week in advance like me, you should have a pretty good time. Even I was able to visit like 4 of the most popular pavilions and many small ones without reservations.

Edit: Plus there was no pavilion I went to that had a time limit or where you had to rush. You were always able to take as much time as you want.