E2E:

As far as I understand, Google wants to treat RCS similar to how it treats web:

1. Have a standard
2. experiment with some extensions
3. learn what works and what doesn’t
4. build what works into the standard
5. repeat

In that case, e2e encryption is coming to RCS.

I know Samsung is also experimenting with e2e encryption too.

Other:

iMessage itself also has more features than RCS. Built in e2ee would be a big one, and aome other more vain ones.

What other notable features (besides e2e which is discussed above) does iMessage have?

[…] Signal or even WhatsApp would still be superior.

(Besides e2e,) What features to Signal and/or WhatsApp provide?

You’re both right and wrong.

Right:

1. Google does have a management problem that incentivizes creating new messenger apps instead of supporting existing services, this has nothing to do with RCS though.
2. Google is trolling Apple.

Wrong:

1. RCS is not a downgrade to Apple’s proprietary protocol (unless you consider sending a laser show screen overlay animation as a specific feature, and not an easter egg)
2. Everyone inside only Apple or only RCS has the same features (message reactions, high quality media, x is typing, seen timestamps, etc…)
3. RCS is open, Apple’s protocols are proprietary. No one but Apple can access their own proprietary protocols. Apple could support RCS if they wanted to. Apple is entirely responsible for the friction between their own protocol and RCS.

Prediction:

Apple will continue trying to control their own bubble to force people to purchase iPhones as long as possible. They will attempt to stall any EU regulations on standardized messaging with deceptive rebuttable that will take politicians time to realise that they hold no real weight. Eventually those arguments will be pulled apart and Apple will be forced to include a future RCS version as a supported fallback. (just like how the EU is forcing apple to allow third-party app stores, and USB-C connections)

I’m on Android, I can see both direct message reactions, ... when people are typing, and see when people have seen my message.

This is all a part of the text message standard that every modern phone follows.

Apple are the only major company that don’t follow the RCS standard.