Mirroring someone's feelings can certainly help, but isn't that critical. Especially since "sharing feelings" is technically impossible unless the Neuralink people have announced something I haven't heard about - fully comprehending how someone else feels about something is a to-be-solved problem.

Eg, if someone is paralysed with grief and someone else comes up to give them a hug, the hugger is probably acting empathetically even though they aren't mirroring the emotion. It is more about identification and choosing an appropriate response. It is a common tactic of high empathy people to respond to negative emotions by embodying positive ones rather than mirroring the painful ones.