As an indie developer, you need to be very efficient with your programming. Coding requires either a lot of time or a lot of money. Big companies or startups have the financial means to lose time and money with their apps because they make money through other activities or because they have solid funding. You, however, need to get a return on your investment as quickly as possible if you want to support yourself with your app someday.
Coding is also only one part of your job and you need to spend a lot of time writing copy or designing app screenshots for the app stores, building your website, testing your app, doing ASO and so forth.
This means it’s not always a good idea to use the shiny new technology being pushed by big tech. With shiny new tech, chances are you won’t find a Stack Overflow answer for many issues you’ll encounter. You’ll also find fewer code examples online to help you. The documentation might not even be complete yet.
New tech itself is also always incomplete, even buggy, at first. SwiftUI, for example, is still a work in progress.
I stuck with Objective-C on iOS long after Swift was introduced for this very reason. It was a good choice because Swift only got ABI stability with Swift 5, meaning anybody writing their app in Swift before that had to rewrite it every year as the language syntax was still evolving! More time spent coding 😬
Uber famously had tremendous issues with their app because they adopted Swift too early. You might wonder why big established company would take the risk to be early adopters. It could be that one of their challenges is recruiting developers and developers will always prefer working on cutting edge technology. Maybe they sacrifice efficiency because recruiting the best developers makes more sense to them strategically.
Of course, this advice isn’t always true. David Smith of Widgetsmith fame is a good example of an indie app dev succeeding because he was on the cutting edge, delivering a widget app the same day Apple introduced them on iOS!
Also, maybe ignore this advice if you’re making an indie app to land a programming job 🙃