> Your broader point about subscriptions being forced into some apps that don't make sense is correct, I just think sometimes people throw the baby out with the bathwater when it comes to subscriptions.
I'm willing to pay for something that I spend a lot of time in it. Clearly the developer deserves to benefit from my benefit.
But I've been burned by phishing, scams, and malware. So I avoid anything that even looks like it. That undoubtedly throws out a lot of good software that I might enjoy. But it also means that the very same software has room to improve.
Thirty years ago, software had demos. Demos weren't laden with advertisements beyond "buy the full product to access this feature!". They didn't have clearly paid-for reviews. Most worked without locking my data after a time bomb expired. Many of those demos resulted in me paying for the software. Some of those demos resulted in me deciding that I didn't like or need the software. The demo fulfilled its purpose.
Way too many demos of games got me to buy the full release of those games. BBEdit, like you mentioned, had a Lite version.
Demos seem to be gone from the modern walled garden.
I can completely understand why some people might be fine with a text editor or todo app that doesn't change much and I'll ceed the point to you that the speed of mobile platforms causes work that might not otherwise be needed. Some of that comes from it still being a changing landscape where technology is improving. Desktops/laptops have not seen as large of leaps in part because they started from a much higher point. For a long time mobile phones had to be pretty limited because if they weren't they'd burn through the battery in no time at all (see: lack of backgrounding in early iOS/Android). I think the desktop platform (Windows, macOS, Linux) started from a much more mature (and open) place and thus it was easier to write something that would stand the test of time. Even then, things like gedit still get updates, nothing is ever really "done".
> Basic text editors and todo apps were solved decades ago.
Yes they were, now people want non-basic versions of both which is was brings up to where we are today. Part of that "required churn" can be blamed on Apple/Google but some of it is due to things that just weren't possible before. I won't pretend that Siri is good but Siri Intents (I think that's what it's called) is a newer (last few years or so) addition and I think it's a decent example of "why would a todo app need a subscription". The platform changes and your users want you to take advantage of the new features so that they can say "Hey Siri, tell Things to remind me do X" (don't get me started on not being able to set defaults). Or, to bring back another example, I might want a widget on my home screen of the next few items on my todo list.
Are these features necessary for todo app? No, in the general sense of "necessary" but yes in the sense of "needed to compete in the mobile stores". Platform churn aside, these new features require ongoing development and subscriptions mean you can roll out a feature as soon as it's ready instead of waiting for the next major point release so you have a list of features worth paying for all a once. Could a developer gate each feature behind a 1-time IAP? Sure but as a developer all I can think of is "there be dragons", that sounds miserable to support.
I do want to address the terminal program point you made. I've used mobile terminal and later mTerm on my jailbroken iPhone. For moving around my local phone's FS it's decent enough but I hated using it for SSH. The UI was just too clunky for mobile which is why I paid for Prompt1/2. I understand the annoyance at paying for something that is free on desktop but I think that misses the amount of work it takes to get a good SSH client on mobile. Could Apple add a Terminal app in the next OS release? Sure they could but unless they put in a lot of work it would be a terrible experience. I'm not trying to pretend Apple is perfect or blameless but I understand the decision.
Lastly, I agree with you that there are some apps that exist that don't require a subscription but one has been shoehorned in. I don't pay for apps like that, I guess I bristled up when you mentioned text editors (to which I pivoted to my notes app, Drafts) and todo manager (to which my mind jumped to Things), both of which I pay via a subscription. Your broader point about subscriptions being forced into some apps that don't make sense is correct, I just think sometimes people throw the baby out with the bathwater when it comes to subscriptions.
PS: If you are looking for linux-like terminal on iOS I would suggest you look at iSH[0]. It's free, open source, and seems like it would be something you might like.
[0] https://apps.apple.com/us/app/ish-shell/id1436902243