One point I'm not clear on with the SetApp model is what happens to Apps downloaded via SetApp after a user cancels their subscription.
They remain working until the end of the final day of the current period you have paid for. Then they stop working.
If a user loses access to Apps obtained though SetpApp after cancelling their subscription, then those Apps would become very expensive.
There's quite a lot of value there if you were likely to have bought 3 or 4 of the apps individually and you only use one Mac. It would not be hard to spend $108 (the annual price of Setapp) if buying the apps individually. Developers often run discount promotions on their own sites but keeping track of them, and deciding which ones you want, can waste a lot of time. Setapp is more convenient.
At the very least, if you have the time to experiment, subscribing for a month or two gives you the chance to try a lot of different apps and discover if they might be useful to you. A lot of people who use their Macs mostly for browsing and games haven't really explored the broader potential of apps.
You could find one or two gems, decide to cancel your Setapp subscription, and buy them directly. Obviously, most apps are available on Setapp are also available for free trial from the developer's own website, but Setapp gives you one interface to browse and install from.
I'm clearly totally unconvinced on the viability of the SetApp business model from the user's perspective
If you have the time and curiosity to learn about lots of new apps, and if you use only one Mac, Setapps provides a lot for ten dollars per month or $108 per year. Of course, you could say the same about Netflix or any other type of subscription bundle: worth it if you have the interest and time to actually use it.
The viability for Setapp is that, out of pure inertia, the majority of users will remain subscribed for years even if they never get around to using many of the apps. That oh-so-human quirk applies to all forms of subscription, and that is why companies love selling them.