Yep, its really a lose-lose for everyone except Apple. Apple could even release a client that doesn't allow Android<->Android iMessage and I doubt many Android users would care. Personally, I just want a decent messaging experience and I would be willing to jump through the extra hoop of downloading another app even if my iPhone using contacts aren't willing to.

Use Signal. Get your friends to do so. What you are describing is a multi-platform ecosystem so don't rely on one of the platform vendors to enable something for everyone else.

Or better, use matrix/element if you can (the backbone technology of Beeper). It's an open protocol not beholden to one central server (Signal/WhatsApp/Telegram/Discord) that could go out of business, get bought, or change their usage policy at any time.