IMHO you mix completely different things. You explain that “fenced container” not needed, because it can be replaced by several things, that not exists now but will be available sometime 
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- Those are needed anyway, it’s a question of usability and preferences. For example, i don’t need lyrics, but i don’t say that line blocks are useless.
- Fenced blocks can be accepted faster, that other. I never said, that those are better or more important. I said, that now we have no containers at all with full attributes support, and it worth to accept at least one type. Then i explained, that acceptance of fenced block is the most easy in terms of time and efforts, not because i like those.