Look at the issue a different way. What functionality needs to be removed from SQLite in order to add more comprehensive alter table? SQLite is defined by being "lite" and that involves a lot of saying "no". You can use other database solutions.

SQLite is also public domain. You can cause this code to be written and have complete freedom to redistribute/keep private as you see fit.

So what is actually being demanded here is that the SQLite core developers spend their time on the feature. SQLite used to have no table altering functionality at all. The ability to append a column (which had few technical risks or ambiguity) was paid for by AOL.