Yeah, the idea that ARC200 didn’t specify the structure just the interface would let the developers decide how they wanted to build it.
The indexer that was built for ARC-72 could be modified for ARC-200 as well. We haven’t gone down that path yet because most people don’t want to automatically view every token that was sent to them. This is why you are getting the outcry for the opt-in to stay. By not having an automatic built in indexer adding an app id works in a similar way to how opt-ins work without the poor user experience. I could see a world where wallets automatically add certain Assets, like USDC, but I wouldn’t automatically add all of them.
The indexer itself would add value adding to something like a block explorer though. Just so it would be easy to discover all Assets created. But I think this is something a block explorer would just build in.