MonsterEnvy
Legend
If Strahd (or any vampire) is reduced to 0 hit points while in sunlight, their Misty Escape trait doesn't function and they are instantly destroyed. The holy symbol of ravenkind can produce sunlight in a 30-foot radius for 10 minutes, twice a day. So a smart party will engage Strahd someplace where he can't easily escape while corporeal, then wail on him, then whip out the holy symbol and finish him off.
Yes that would defeat him. But the problem is engaging Strahd or preventing him from running and waiting out the clock on his weakness. (Also finding the Holy Symbol as it can be in a lot of different locations) Added on the party does not get to pick were Strahd is engaged. They can find him in one random location. The rest of the time he will appear out of nowhere and ambush them picking the best times. (He is also pretty guaranteed a surprise round.)