Many apps I used are moving to a subscription model (a.k.a. Software-as-a-Service in the corporate world). As they move to the SaaS model I take a deep look.
Immediate red flags for me are when devs explain their move in these ways:

• Implemented a custom proprietary sync mechanism
• Implemented encryption
• Costs are rising
• Push notifications (in most apps, unnecessary chrome)
• Theming, styling, icons &| dark mode (again, unnecessary chrome)

There are select apps in the subscription model to which I subscribe and why:

• Apollo (Reddit reader app): superior to the native app & other options; theming; and to support development
• CARROT Weather (Weather app) Tier 2: additional data sources; Apple Watch; map layers; and other stuff
• Fiery Feeds (RSS reader app): for “Smart Views” ; to support development; and I read a lot of feeds
• Overcast (Podcast app): to remove adds; to support development; and I listen to a lot of podcasts

Apollo violates two of my red flags, yet the developer is crazy responsive; his app is heads & shoulders better than the native Reddit app; and he regularly pushes out updates for security/bug fixes/functionality/chrome.
CARROT Weather also often pushes out updates for security/bug fixes/functionality/chrome, and is also better than the other options.
Overcast does, too, but more judiciously based less on chrome. I like PocketCasts, too, but less so.
Some apps that I avoid in the subscription model but use in their legacy or alternate license mode:

• 1Password
• TextExpander
• Drafts