The devs were hoping that they can keep their apps up and their livelihoods without too much additional work, that’s fair from them I suppose. But they should definitely be taking a hard look at porting their existing apps for the Fediverse, if they aren’t yet.
This is already handled by Firefox’s very own Multi-Account Containers extension.
I like to add Sticky Window Containers for extra functionality. Sidebery also works well with containers.