can unrealistically only miss the target but not the ground the target occupies
Sure it can ... if you dodge that ball of fire, it misses you ... if that ball of fire explode in next second both the ground and you will be on fire.
Do you really think that someone who can create ball of burning plasma in his bare hand cant control it anymore once he throws it? Think again.

like spider webs where the Spider Matriarch gets over 40 falling dmg
I destroyed that web with single arrow ... same result, no firebolt included ...
I dont see your point here. O_o