Welcome to the forum, mwyman. I’m sorry you’re experiencing a hang. As Marc, says, Setup mode operations on larger templates can take a few seconds to complete, but the software shouldn’t hang, and when the template is empty of music you should also find that each edit takes only a second or two. If you’re really finding that Dorico is actually hanging, please sample the process in Activity Monitor and zip up and attach the resulting sample.
You can run Activity Monitor via Spotlight, then find the Dorico process in the list of processes, and click the cog button at the top left corner of the window, then choose Sample Process from its menu.
If the program is really hanging, I’d guess it could be playback-related: Dorico might be trying and failing to load sounds for some reason. If you create a small project with just a single instrument, e.g. from the “Solo piano” template, can you input notes and hear them played back?