Surely a good palatable house wine (of any colour) is the mark of a good restaurant
Indeed. Especially as restaurants are wise to the oft recommended 'pick the second cheapest wine on the menu' 'tip' when people are afraid of looking cheap by ordering the house wine. The second cheapest is likely to be the most profitable, but the house wine, which would be seen as a recommendation by the owner, should be decent value/quality and well matched to the style of food on offer.
I don't know anything about wine and am not particularly fussy. But what I do is that even so called 'experts' are unable to reliably tell between cheap, medium and expensive wine, so to me that just says it's all subjective and the 'you get what you pay for' rule absolutely does not apply. Just drink what you like and if you get the odd dud, it's not the end of the world.
Some years ago, we stayed with friends who live in Spain. The bloke's parents had been there just before we got there and had left behind some wine that was quickly polished off. We all agreed that it was quite nice and we said we'd get some more when we were in the supermarket.
Friend said his DF was a bit of a wine snob, so warned it might be a bit expensive. So we goes along to supermarket to find that the 'quite nice wine bought by mates wine snob DF' cost all of FORTY NINE CENTS A BOTTLE.
. We may have bought a few bottles more.