Having owned Audi, BMW, VW, Toyota, Honda, Infiniti, Ford, Volvo and a Mercedes, and been to all those dealerships - I can't say I care a whole lot. First, you spend so little time there as % overall car ownership life. Second, some differences are barely cosmetic. My current 'Audi' service center has different front offices but the same workshop behind for Audi, VW, Kia and Porsche. Yes, getting a loaner used to be easier at the 'luxury' brands but even that doesn't hold up any more. Yes, the Merc dealership was super shiny and flashy but I cant say service levels were much different.
Lexus is an interesting case. It did start as a completely differentiated brand - sort of like VW vs. Audi - with cars build on entirely different RWD platforms etc. Same with Nissan/Infiniti initially. But over time, everyone has come to realize to cost savings and $$ benefits of the Honda/Acura model. Build the same car, add some padding and slap on a new badge. Honda was even shameless enough for a while to sell the same cars as Honda in US and Acura in Canada.
So now the entire industry has moved to the same model. Toyota probably puts in the most additional work to upgrade the Toyotas to Lexii (?), while the newer Infinitis are mostly worse than their Nissan underlying IMO.
The last holdout has been VW/Audi - and even they have thrown in the towel. Going forward the Audi line will be split with A4/A5 being build on VW platform (A3 already is) and A6+ on the Porsche platform.
The lower trims of 'luxury' brands are absolutely the worst value out there. There is nothing luxury about them - they lack many features available in mid/upper trims of mass market brands. So yes, it is an ego exercise.