If there is an issue with canonical tags and we can fix it (little work/volunteering) that would be great.
Customizing canonical was discussed, but it was said that now that we have routes.php it can be done without touching the canonical.tpl file. Nothing about issue with canonical tags.
As I’m not sure what you mean by "difficult to use", (in my mind the canonical tag is the "real" url of the page; https://en.wikipedia.org/wiki/Canonical_link_element) I suggest you edit this page and add a paragraph for the issue you want to address.
anything we can improve is good for our health. 😊