They actually show great promise for various conditions such as cognitive decline. You should check some of the work by Dom D’agastino on this, even though he is affiliated to a supplement company.
I am a keto nerd and have 2 tubs at home. Had them for months and I’ve only used it twice as they’re expensive, not the holy grail, etc. However, they’re marketed as the holy grail and that is greatly misleading. It’s actually sad that a decent product is being sold as an ‘instant fix for ketosis’, which is patently false. Otherwise, it can be useful for performance, transitioning, etc.
I hope to give them a proper trial at some stage using PSMF with higher training frequency and volume than normally recommended on low calorie intake to see what it can do. Otherwise, I agree with you about generating ketosis through diet. I did blood test after one ingestion and got a 0.8mml ketone reading. Not deep ketosis, but to be fair that was also post workout and after ingesting whey. Recently I tested at 0.9mml after a few days on PSMF alone so it shows exogenous ketones, or even MCT oil and other supplement, are not required for significant ketosis. Just my thoughts.