Shit isn't made like it used to be.
Or in my case a 5 box of 8oz mac and cheese is now a 4 box of 7.25oz mac and cheese.
So yes. Same goes for most things physical not just food. Clothing is made cheaper or pay through the nose, Furniture is made cheaper or pay through the nose, etc etc. The things that actually matter are in decline. Or are you one of the smartphones = awesome standard of living types.
My grandparents love to tell me about how they only had one pair of shoes as children, which of course were only for church, along with one pair of "dress" overalls to wear when they weren't wearing the stuff their mom made for them. I'm sure those shoes and overalls were of very good quality, but they were also so expensive that no one got more than one set. That set was also to be guarded carefully to ensure that it lasted as long as possible. I'm also sure their parents would have loved a cheaper option so they could wear them for more than one day a week.
I think that's the difficulty with comparing quality over time. Often back in the day the cheapest choice was of excellent quality, but it was still expensive. Nobody complained because they didn't have a plastic made-in-china version to compare anything to. They just bought less and took better care of everything because that was what they had to do to make ends meet. Every pair of shoes, every suit of clothes, every dish or pot or pan was still a significant purchase money-wise though.
So no, I don't see a real decline in quality for money spent, just more cheap options. If you spend the same money, adjusted for inflation of course, you're probably getting even better quality today. A $15 pair of shoes in 1960 is a $120 pair of shoes today. Neither would last me much more than a year, but the shoes of today would be far more comfortable. A $2500 car in 1960 is a $20,000 car today, and the car of today will typically go several times the distance of the 1960s car without significant repairs while being much safer and using less gas. This is the way it is in most categories of product. You can't be mad because the cheapest version of something available today isn't as good as the cheapest version of something in times past. Chances are that item was priced the same as a higher end item would be today, and was actually of lower quality than the comparably priced item of today.
One of the reasons our parents and grandparents are the miserly old fucks they likely are is because, while everything was pretty good quality, everything was still
expensive back then. Imagine if you HAD to buy the $200 shoes, or the $20,000 car, or the $100 shirt, or $80 frying pan because there wasn't even a cheaper brand on the market. Now imagine that you had even less money than the average working person does right now to buy all that with. You'd probably start acting a lot like gramps in that situation. Everything you bought would last, but then again it would have to because you certainly couldn't afford to buy it all too often.