That’s the point. It’s not Apples problem. Apple supports basic carrier messaging. If someone buys an Android, Apple users can message them just as anyone who buys a Windows Phone or BlackBerry.
It’s either an Android problem — getting fragmented service and no E2EE — at which point don’t buy an Android; or a user preference problem — “Inprefer iMessage” — at which point buy an iPhone.
Vendors on both sides have gone up and down the market to cover the spectrum, it’s not even a “can’t afford the premium feature” problem anymore as it were decade ago.
Again, Android problem, not Apple problem.
Apple stated clearly they’re keen on working with GSM Consortium (who owns RCS and has more sway on carriers than Google does) on bringing E2EE to the masses.
If Google’s reputation of finding new and exciting ways to sell targeted ads doesn’t precede them, then they might have a better chance of getting a first party solution like Apple does with iMessage. But alas, Apple is not responsible for Google’s business plan or public image, and that problem is Google’s to solve.