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.
The issue is WhatsApp from a few years ago versus WhatsApp today - meta/favebook is probably the worst possible company to have bought it, their record on security, privacy, and features is horrible.
The app today is full of enshitification (meta ai being shoved down my throat by the communication monopoly) and nobody can ever fully trust their security or privacy because its not open source.
Signal sadly doesn't yet have the ubiquity of whatsapp - but for everyone that has it (now I'm finding even non tech-savvy family are switching over) use signal, and where you have to, use WhatsApp.