Yep, this is such a huge impact on the apparent inflation rate. It is an absolutely valid thing to measure, but I love your point about how the market has essentially shifted to only selling luxury products. You either get to pay luxury prices or do without.

Other challenges with CPI are substitution and owner's equivalent rent.

With substitution, economists look at changing purchase patterns and adjust the basket of goods included in the calculation. For example, if you used to spend $20 per week on steak, but now you spend $20 per week on chicken, the economists say your preference changed and there was no inflation. In some cases, this might be true, but in others it could be that the price of meat went up significantly and you switched to something cheaper because you can't afford the higher prices. If you're talking about the fact that nobody is buying 8-tracks anymore, then substitution is certainly valid, but that's not always the case.

In the case of housing, up until the early 1980s, CPI included home prices in the calculation. Then they switched to an estimate of what you would pay in rent for your house rather than the price of the house. This flattens out the CPI movement when home prices go up and down. Is it valid? Maybe? Probably to the economists at least, but not to anyone who wants to buy a home. On the flip side, if you already own a home, home price inflation is kind of irrelevant in the short to medium term because your cost doesn't necessarily change (other than insurance and taxes).