Sadly I think this is just another case of product adoption largely being driven by techies in the early stages because they loved it, and later in its growth stages realising their market is now way more mainstream and designing their features as such. And now we're alienated by the same product we helped spread.
Twitter is another obvious example I can think of.
Nothing to do with self respect This is a completely accepted and promoted way of growing your product. See for example the strategies outlined in “crossing the chasm”. Techies are in this case the early adopters, and now that slack has crossed the chasm, they are targeting a completely new user group, the early adopters, with a new set of needs and wants.
Time to move to a new product which still focuses on techies.
As a member of user minorities - the "tech savvy" niche and "knows software can be ergonomic, and expects that" niche - I'm already avoiding using new "innovative" products. The story is always the same - people with needs are used as tools to drive initial adoption, and then the product self-destructs trying to chase the lowest common denominator.
FWIW, I wouldn't even be using Slack if I weren't forced to, like probably most of its users. Regular employees don't have much say in what companies use for chat, nor do most people in communities in what tool was used to start them.
I'd do it for a boatload of cash but not any less. Your core tech users are still selling your product for you, free of charge. Unless it's abuse/fraud/security mitigation there's usually a way to keep your technical customers happy along with your new user base. It obviously has a cost but if you're making dramatic changes that alienate your early adopters I'm sure that those changes are going to do some needle moving in terms of increasing your profits. No one would do something like that on a whim...
That cost does need to stay within reason though. And something crazy like maintaining divergent architectures/infrastructure isn't really reasonable either. But on the bright side the technical folks might be understanding of these sorts of tradeoffs.
Why not try to satisfy both kinds of users? Options and customizability are a thing. One-size-fits-all seems to be the current software trend, but it wasn't always like that. Maintaining a piece of UI that was already there shouldn't be that expensive.
They don't have to. It can default to simple behavior, with the "techy-friendly" options hidden behind a "Settings - Advanced" menu or tab that regular users won't even visit.
Twitter is another obvious example I can think of.