'I'm not a old angry man who thinks he knows everything.'
I am though. (Actually I do NOT know everything, that is what prevents you from learning more even at old age.)
And hearing the rest I'd have to say there are still some skills to pick up there. For one, if people would simply change the oil with some type of regularity there would be pretty much no deposits to do things wrong anyway.
Amazing things? ANYTHING that cuts deposits that quick will be a SOLVENT and enough to cut HARD deposit loose is WAAAAYY more than enough to cut the oil film strength, you are killing engine life every time you use it. And if cutting hard carbon give a second's thought to what diamonds are made of and where that hard carbon is going to end up. It eats even the exhaust valve seats, by far the hardest parts in an engine.
There may well be a time or place to use something like that OCCASIONALLY and based on need at the time but doing it as a ritual?, hey, the salesmen of those products will tell you the same thing in a dark corner (I used to push them there) but to keep it 'their little secret', they want that money the unlearned pile on over and over.
'I have seen them massively reduce oil burn off...'
Yes, you dump basically glue into the engine after running water thin 'fuel saving' oil for most of the engines' life to wear it out prematurely. Run slightly thicker oil (no extra cost) and NO thicker additives and count the money you saved to get to the same place. I believe the extra end of life running more than makes up for the slight fuel costs incurred running the thicker oil. The engines certainly do not break and they don't smoke either. Using absolutely NONE of that.
Of course, yours and do as you will..........