I think that this is shortsighted. It is a new area and there is a lot of work improving the effectiveness of these things. If somebody told me that ROP was totally impractical for a plethora of reasons when it was first proposed, I would have believed them. Now, we've got completely automated tools to generate ROP chains without hardly any access to a binary whatsoever.

These sorts of attacks will get more sophisticated.

Side channels through miss-speculation also have a fun property of being virtually undetectable since the problematic code never actually executes. This is attractive for very powerful actors who might want to spend the extra effort for the covert attack even if there are simpler exploits to actually launch.