I honestly hope someone will read this comment and vibecode an Atlassian 2.0 platform, preferably open source. But really, I will take closed source and paid as well - just give me something that's on par in terms of features and integration but without the terrible UX.

To be clear, I agree with the terrible products part - but currently they are not dying because there is no alternative platform which is flexible, scalable and feature-complete enough. You may find alternatives for niches, like GitHub for software engineering, but the Atlassian stuff allows for knowledge transfer and familiarity across many many domains. I've seen it used anywhere from government burocracy to customer service and construction companies. They nailed the abstraction for flexible issue management, just the implementation is terrible.