There is an outstanding explanation from Google’s John Mueller about the differences around the noindex and rel=canonical signals and why they should not be mixed. In short, Google wants clear signals that are consistent and straightforward. When you start to confuse Google by communicating that one URL is more important than the other, but another signal says the opposite or you use the noindex to hide pages that you think are less important but want to pass that weight to other pages – it can ultimately confuse Google and come back to bite you.

Google’s John Mueller explained it super well in this Reddit thread, read it for yourself:

Forum discussion at Reddit.