They also want you to believe that new stuff is better than old stuff because it's the new stuff they want need to buy. But is it?
If people buy it and remain happy with it then pretty much by definition yes. Naim used to achieve this in spades and it is still continuing to a fair extent as demonstrated by posts in this and other Naim threads.
Is an amplifier built today really much better than one built ten or twenty years ago?
It depends on what is valued. Some value new highly, other value old highly, some value technical performance whereas others consider it irrelevant, etc... It is unreasonable to criticise Naim or any other expensive marketing-lead luxury brand because they offer low technical performance for the money. This is not what owners of Naim-like hardware value and why should they if it doesn't interest them? They will of course normally consider the hardware to have high perceived/subjective performance for the money or else they wouldn't have opted for it.
Another thing that they rarely mention is that there is a huge amount you can do to improve the way a system sounds in your home without spending very much, if anything.
Again this is missing the point of what people that purchase Naim-like hardware value. There is every chance they will derive most of their enjoyment from multiple boxes of electronics, turntables, DACs, etc... along with a relatively modestly priced pair of small 2 way speakers in an untreated room with their head on a comfortable high backed chair/settee flat against a wall. This isn't appropriate if a high technical sound quality is required to do a job but this isn't what is going on. It's about enjoying one's hi-fi while listening to music and that depends on how a person is wired up internally and what they do and do not value.