imessage is no better in that case - and outside America barely anybody still uses either SMS or RCS, apple is a smaller share of the market meaning the ubiquity of imessage isn't there.
If you want anything beyond SMS which is a universal standard, you both have to be using the same service - I'm just saying that signal is available for anyone who wants to use it.
I was also upset at the removal of texting from signal, but in hindsight its for the best - if its a secure message service that youre not charged per message to use, the support of a dying platform which is difficult to distinguish when in use is an issue - now its extremely clear whether youre reaching someone through signal or text, cause signal only sends signal messages.