All of the services that either just started or haven't even launched yet seem to not understand the concept of market saturation. Was there ever a demand for Discovery+? I enjoyed "Fixer Upper" but never once thought, "They should build and market an entire streaming service around this show and "90 Day Fiance" spinoffs." I think these studios think they'll steal customers away from Netflix since Netflix will start losing access to other studios' movies, but I'd rather watch "Ozark" over a "Frasier" reboot on Paramount+ or a "Punky Brewster" reboot on Peacock. Why pay for rehashed ideas and old episodes of shows that are in syndication. I can spend all weekend watching "The Office" on Comedy Central if I want to watch it that badly, so what are these services doing to earn my subscription money? At least Universal cut a deal to get the WWE Network on their platform, so they'll have a decent number of subscribers who may not even care about what else is on Peacock as long as they have their monthly wrestling pay-per-view events (and - if you don't mind commercials during pre-recorded shows - at $5/month less than the WWE Network was).
I don't think services need a lot of original content to draw subscribers. Disney+ largely consists of catalogue titles I already owned, but it's still worth the monthly fee for just the Mandalorian and then WandaVision. If a digital movie rental is $7 on iTunes, I'm not going to balk at $9/month for Disney+, even if the original content has been minimal thus far.
Likewise, Paramount+/CBS All Access has probably done well with a handful of originals, but Star Trek in particular is probably enough to draw subscribers.
As everyone launches their own service, it's getting to the point where subscribing to everything will cost the equivalent of an old school cable subscription. Will some fall by the wayside? Maybe. But, I don't know the finances of these services. They're probably much more profitable than the traditional television model. Charging customers directly for the content means more revenue per viewer, versus selling advertising time (I think). A show that would get cancelled on network TV can now generate enough revenue to survive, especially for those properties with a dedicated fan base.
Disney+ has 94 million subscribers, which puts them in the $600-700 million range monthly. It costs them $50 to $100 million per month to produce the two main series to date, so I'm guessing the profit margin is much better than broadcast television.