There is essentially no reason to use an alt store unless you are looking to explicitly pirate or Google isn’t operating in your area, sideloading APKs from the web is a very good way of turning your phone into someone else’s phone based on how many of the APK aggregators are injecting malware into their downloads.
Android is a viable system however to use it securely as a device that has your life on it you are going to have use it as a walled garden or spend countless hours doing everything yourself.
And the overall experience will be worse especially when higher end devices cost as much if not more than an iPhone.
I hear those points, but none of them make Android "walled garden". "Walled garden" requires lack of user options re app sources, such as what iPhones do, and Android has many non-Google app sources.
The fact that dogma1138 did not find any of those non-Google app sources useful does not make Android systems a walled garden.
I know of Linux systems whose users only ever install apps from default repositories. I know of Window systems which are set to only allow apps from app store. This does not mean they are closed, it just means their users do not need more.
Android is a viable system however to use it securely as a device that has your life on it you are going to have use it as a walled garden or spend countless hours doing everything yourself.
And the overall experience will be worse especially when higher end devices cost as much if not more than an iPhone.