Where it is made is critical. You can't seperate the politics from the manufacture when talking about China and Russia. The mindset of the places you mention is to do it cheaply as possible, its a way of life for those cultures and its impossible to get consistant quality. Furthermore a few internet searches will enlighten you to the poor pay, long hours, no workers rights and terrible human rights of places like china. It endemic in the manufacturing for such states to do it cheaply and make the biggest margin possible for the owners.
The concept of copying and ripping off is second nature. Taking British brands and moving all the manufacture to the far east, trading on the British names of former British brands with no DNA of the original design or mindset left in anyway.
Personally I find that loathsome, coupled with the way the workers are treated and the regime they suffer, means buying those products you are financially supporting that process at the same time killing UK manufacture.
If what you say were true about it doesn't matter where its made, why are all these chinese brands sticking half baked union flags on their products and pretending its still British? The answer is obvious, it really does matter and it matters alot to most people.
You're right in that buying British won't guarantee quality but in Hifi circles it really does guarantee it, because the true British brands couldn't survive against the unfair advantage of basically free labour, no green taxes etc that chinese manufacture has by comparison. The only way you can survive is being much better than the eatern offerings because costs are exponentially higher.
Most chinese built manufacturers are so desperate to convey the illusion of British made they put union flags on their products and in tiny writing underneath "Made in PRC" the name is so toxic that dare not mention it directly.
If I were a betting man I would bet with amost certainty that a 100% British made piece of hifi will be infinitely better than those churned out in the eastern sweatshops with a faux union flag on them.
If you expect a dealer to guarantee the quality of a product you are naively mistaken, the industry doesn't work like that. This is exactly the point the eastern manufacturers don't really care about the quality they want the cash and they do just enough to keep it flowing, they consider their products disposible and to them they are because they cost virtually nothing to make, so even if the QC is terrible they can just ship replacements until one that can outlast the warranty is delivered.
Nothing more, nothing less.
Where is made for hifi is literally the be-all end-all of the industry.
I wouldn't want a Bentley made in China, but it seems you would be ok with that.
Its a bit like buying a house, three most important things, location, location and of course location.