Just going to focus on the customer service side of the argument.

I would argue that customer service across the entire airline industry, if not the broader English-speaking universe, has declined over the last few years. Companies rely more on computer systems of limited functionality, outsourcing of customer service to cheaper countries, and AI, and less on empowered and experienced people. Those aren't new trends, but COVID accelerated those changes. And they aren't the only ones. BA closed their US call center and doesn't empower agents at airports to book and rebook flights, insisting on guests using MMB or calling BA instead.

The other issue is that self-service tools, while still struggling at times and inconsistent from airline to airline, have also gotten better over the last decade. As a result, I suspect that a higher percentage of power user interactions with customer service are in meltdown scenarios, when you're most likely to encounter unhelpful or overwhelmed agents.

As with so many other things (I just read the IT thread), DL doesn't see investing in customer service as valuable or likely to produce a meaningful return, so they don't do it.