One idea, but people will probably hate me for it:
If you return to e.g. the google search site (hence: when the long click metric would be triggered) have a dialog on top saying ‘result great / OK / bad-or-confusing’.
Can probably be gamed (bot nets trying to destroy the reputation of others) but at least a long time would not automatically mean ‘great result’. (In the arms race to combat destruction, it could be so that a ‘bad-or-confusing’ click would not actually push a value down, just not make it go higher).
Kind regards, Roel