Anim Zmiros actually takes the pains to explain how it is only a vision and not a depiction.
If you don’t think Machnisei Rachamim is telling the Malachim to do what is actually their job, what is it? The question is only the tone. There is no doubt here, if you understand the words, that it is not asking the Malachim for any Parnasa or success. It is about bringing our Tefillos to Hashem. That is their job. Is it praying to them? Good question.
We do know that we never pray to angels, and that for some reason even that Piyut is specifically on one topic. Those who continued this Piyut obviously didn’t think of it as praying to an angel, since they never engaged in that type of thing. When I say it, it is as the Maharal explained that it is not Tachnunim but rather a command. And if I wouldn’t know of this Pshat I would either have another Pshat or I would have a Kasha. But one thing I know it isn’t, a prayer to angels.