I think standards were very different back then. Probably a lot of their food would be infected and sour, but since that's the way everything was, it didn't generate much notice. Add in the fact that even if infected, beer was safer to drink than water and hey, it had alcohol!
Yeah, but who says sour is automatically bad? Not lambic brewers, that's for sure.
I definitely think you can make good beer without any tools, but I haven't done a 10 year apprenticeship to figure out when the water is the right temp for mashing
With some math though we can figure it all out to hit temps no problem, something that brewers probably figured out through trial and error. You can heat water to body temp, that is easy to feel. Then you can add measured quantities of boiling water to hit whatever temp you want. Physics works, even if the brewers way back when didn't understand exactly why or how.
There were probably good batches and bad batches, and the brewers who made more good beer than bad were probably more successful. It might have been ugly, murky, chunky, but that doesn't mean it was bad
, just different. We'll just never really
know what successful brewers were making 2000 years ago, despite residue found in old jars.
I've been to China and eaten a lot of different foods, and I can say without a doubt a lot of it was delicious and some of it was terrible. But the people I was with liked it, so it was good to them. And beets taste like dirt to me, but my wife loves them and that's fine. So I don't think we can assume that ancient beers would be terrible, especially if you were brewing for a king/pharaoh and your life depended on making good beer