Why might Finder appear broken with question marks in the toolbar?

Those seem to be missing apps.

You can "fix" it by removing them:

Press the command key and click the item, move it out of the toolbar until it vanishes.

If you need to find out what those items may be, take a look at the system log:

open /Applications/Utilities/Console.app

Check the System Messages (all) and try to click one of those question marks, because you have a hang, the system will log it.

Either the preference file where these icons are stored has become corrupt (less likely) or the items that were placed in the toolbar are now deleted or moved to another drive (most likely) or your directory is corrupt (least likely).

To fix these,

• edit the toolbar to remove the question marks / restore items as desired
• reset the toolbar to defaults (less likely)
• run disk utility to repair or erase / restore the Mac. (least likely)

To learn more, search for toolbar in the finder help menu - you'll see the command to edit/rest as well as more graphical help on how to manage the toolbar.