To add to that, in most countries iMessage has irrelevant market-share and I know people who don't even know what that word means (we tech people live in bubbles). So an Android iMessage is not really sought after in most places anyway.
iMessage is a service that allows your phone to connect and send messages to other iMessage users.
Use email if that's what you need. Nobody forces you to use iMessage/Telegram/WhatsApp/...
The EU strongly disagrees with this statement in case of the the latter two, which is why they are being targetted by the DMA and must provide interopability so that you cannot continue to be forced to use them.
If iMessage had users in the EU, the same would have applied there.
Being forced to use something does not mean you are being held at gunpoint or that no other options exist. For messaging apps, being in a location where your entire social network uses one app is indeed a case where the average person ends up forced to use that app as picking another option means not talking to your social network (unwanted) or having to convert everyone else (unreasonable). This harms both competition and users.
I think that clearly marks the end of any useful discussion.
Assuming you are just misunderstanding. The comment about iCloud email is talking about interoperability. Where someone with a gmail account should be able to send an email to someone with iCloud account. And vice versa.
The argument is that it is not OK to prevent this sort of interoperability, and requiring this does not mean you have serve the users of other services with servers and hosting, you just have to allow WhatsApp to send messages to imessage and vice versa. Just like email