I'm personally loving going slow these days (as someone who's crashed and burned in the past).
But, I can see how being at a standstill pace could be crippling. I guess it's a problem if either the person holding back is doing so manipulatively... or if it's hindering growth for either person. I'd say it needs addressing if the person is avoiding something by holding back...
and you find yourself being asked to wait or doing it of your own accord, holding so to speak, to find out is there was a possibility the relationship could be mended either in friendship only or romantically in a poly relationship ... would you? or would you let go, walk away, cut off all ties, and never look back?
I think this is something only you can answer. If there is something in it for you, then it's worth mending. If you feel uncomfortable waiting, or if the waiting seems like a hindrance or a sacrifice you're not willing to make, then you have another decision to make.