"It's long." and "It's a meta thread." are both simplified versions of the actual objections. The full versions are "It took too long to come to a point so I gave up reading" and "It's the umpteenth meta thread in the last week and I'm tired of them", respectively.

You'll note that the three-times-longer post you link to goes to great lengths to summarize its key points in the first few paragraphs. The structure of the post is also clear, and there are even three separate objections that people can read and address individually. Also, part of the "length" argument might be that you have page-long paragraphs with no breaks in them, which is harder to read.

Likewise, the growth post is a different kind of meta thread. It starts a new discussion and has data to back it up; although I disagree with pretty much everything in it, I saw no reason to downvote it. On the other hand, the current post is just rehashing the endless discussions we've had over the past few weeks that doesn't seem to bring many new points to the table. When people say "we don't want a new meta thread" they mean "we don't want a new thread to discuss the same things that the last three meta threads were filled with."