"It IS the fault of panic buyers."
I'm really not convinced about this. I usually do an online order about once every 6 days. In addition, DH or I pop to our local store at least a couple of times a week to get extra fresh items like berries, milk, bread etc.
However, online shopping slots have been scarce for a while, even before they dried up completely, so my last two shops were 8 days after my previous one (my next one isn't for 2 weeks). The first was before we went into self isolation but I had taken the decision to avoid popping to my local store as much as we were already conscious of the need for social distancing. So, for example, I bought enough milk for the whole week instead of my usual 4 days worth. The second order, arriving in the middle of our self isolation, was even bigger as we needed it to last for well over a week.
I will be going to our local big Tesco on Sunday when I'm out of isolation. Again, to avoid constant trips to the store, I will buy enough to last the full week, or even a little more (unless there are limited items on the shelves).
Also, I usually have breakfast at work at least 3 times a week and tend to buy a sandwich or similar for lunch most days. DH does the same about twice a week. DH takes the DS for dinner after swimming once a week. I usually meet a friend for dinner at least once a week. These are all meals that I now have to buy for, and it's a significant amount. So my shop WILL be bigger. It's not panic buying.
Panic buyers who bought 50 packets of spaghetti were annoying and stupid. But I don't think they're the problem. It's the fact that we all genuinely need more food in the house to get us through a week and to avoid the day to day trips to pick up a few bits and pieces that is causing the shortages.