He got his ass handed to him by a stormtrooper with a crowd-control staff. If Lando was in a gunfight, you wouldn’t take away his blaster and give him a lightsaber. For some reason Maz had faith Finn could use the Jedi weapon, or she’s got a weird sense of humor.
I don’t get why this is a problem. Finn could use the saber but he was not as skiled as that stormtrooper or Kylo, that much is clear. This all makes sense.
Would this make you happier?
Finn “I need a weapon”
Maz “Ok, hang on, ill find you a blaster. There’s one around here somewhere.”