Why won't Mercedes let owners open the hood? [video]

I disagree. Mercedes used to be well known for reliable and easy to repair cars among the general public, or at least that was true among the people I know. E.g. there are stories about old mercedes with millions of kilometers, some of them in remote places and owned by workers (e.g. taxi drivers). Of course, this is no longer the case and newer models are very disappointing in this regard.

Also the right of repair is orthogonal to the concept of luxury. What is relevant here is whether mercedes is leveraging their market power during the car's design phase to hinder competition in after-sales services and profit from that. Those decisions could have negative externalities for consumers and the environment.