Do you really think that at 3 star restaurants, where they have about 5 staff per customer, they would serve Nespresso if they thought it isn't good coffee?It doesn't matter what I think, you can read what they said. Of course it's not Starbucks quality level, but it's not great coffee, just good enough for the other qualities to win over better tasting coffees.
Can you show me any evidence that better coffee can be obtained in a reasonable other way?
Sure, the way multiple coffee shops do so here: you buy a decent Italian espresso machine (such as a La Marzocco), you get a few baristas with a couple of decades or more of experience serving coffee, buy decent beans and grind them yourself daily.
Of course, this isn't reasonable if you're a restaurant which serves a few dozen cups a day, which are just a small part of the whole "product". But for a dedicated coffee shop, which might serve more than a hundred per day, the costs are reasonable.
I know it is romantic to think that you can make better coffee yourself
I didn't say that. I have a capsule machine myself. But I don't need to make better coffee to know that better coffee is made.
Nespresso burns and grinds and vacuum seals coffee that is then placed into a machine that delivers a fixed amount of water at a particular speed and temperature. All the parameters in this process have been tuned by professionals backed up by panels of taste testers.
Sure, Nespresso is a great value for its price. But nothing in that process is better than what I'm describing.
Why would a restaurant be able to do better, let alone significantly better, at a reasonable price and effort?
Not restaurant, coffee shop. And I don't know what you consider "reasonable". The reason they do better is because they have different constraints in terms of space, marginal costs per cup and importance of the coffee to their line up, which allows them to invest more in it.
Coffee simply doesn't have this.
Grinding many days in advance, even if vacuum sealed, does have an effect on the taste.