1) you said you had to pay, that’s not true.
2) you said you needed source code and to compile, that’s not true.
3) you said you “can’t just go online and download an app”, which unless you’re being very pedantic, isn’t true. I even gave a popular example, iSH.
OP didn’t ask if alternative app stores existed with one click installers, they said you should be able to side load apps on iOS, which I’ve shown true via multiple methods. If you had “said exactly the same thing” I did, then you must have a different definition of the phrase “you cannot” which is the lead of your comment which I’ve shown to be factually incorrect.
At the end of the day, you can't just download an app and install it. You have to go through hoops, all of which involve money, expirations, or limits.