Try these:

1.  Show them Scotty’s videos on Cadillac and    GM, if they haven’t seen them already.

2.  If they still don’t listen, let them know the engine in that 2021 MY (6.2L V8 L87 Ecotec3) has cylinder deactivation (even more complex than the previous generation of this technology with 2x the cylinder deactivation hardware as before, and that previous generation already had issues) and can potentially wear out/damage the engine over time, and is also direct injection-only so susceptible to carbon buildup over time on the back of the intake valves.  Also, let them know some of the L87 engines had been subject to recall due to broken valve springs (quality control issue).  What’s to guarantee more engines outside of that timeframe don’t still have the issue?  Link: https://gmauthority.com/blog/2020/09/new-service-bulletin-addresses-valve-spring-issues-in-gm-v8-engines/

Also, show them this article on potential 6.2L Ecotec3 V8 issues:

https://chevytrucks.org/chevy-ecotec3-6-2l-engine-problems/

Then, mention to them it uses the Ford/GM co-designed 10-speed AT which already has had issues and there is already a class action lawsuit against Ford.  GM already had issues with their 8-speed AT but now going to 10-speed only increases potential for issues.  

Finally, mention the all new Escalade is the first year MY of a new generation and has lots of bells and whistles including the largest OLED screen in the automotive industry and being a first year will invariable have bugs/issues and if they buy it they will be guinea pigs for Cadillac, and they aren’t even getting paid by Cadillac to be a beta tester!  GM quality has been going downhill for a while now; what makes them think this first year of a new generation will buck that trend?

3.  If all else fails, just tell them to at least lease the vehicle under warranty and turn on before the warranty expires.  There is lots of tech on the new Escalades and out of warranty well cost a small fortune to repair (and GM is not known for their electronics).