I have never found these arguments compelling. They are obviously not true (e.g., itertools.compress() added in 2.7/3.1), and so what I really hear is: "I don't like it and I outrank you."
That certainly contributes to it - if you are not a committer, you have to find a committer that finds the feature important enough to work with you to integrate it.
Fortunately, there is a process to overcome this problem: the PEP process. If you you really really want the feature, and can't find a committer that supports it yet, write a PEP. Then it will be up to Guido van Rossum to reject it.
The same reasoning would seem to apply here. In the OP's example, the meta-decorator becomes opaque due to the use of a lambda. If one could introspect a compose(), then introspection tools could actually know the set of decorators being applied. As it is, the "preferred" method of using a lambda actually makes it quite hard to know anything.
That makes it even more necessary to write a PEP. I would have never guessed that introspection on the compose result is desirable. AFAICT, operator.attrgetter isn't introspectable, either, nor would the patch proposed in #7762 give you an introspectable getter.
ISTM that people have fairly different requirements wrt. that feature.