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.

The spell is fire
bolt, not fire
ball. There is no exploding. It's more similar to a crossbow bolt than a grenade.
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
Did you shoot the web directly with the arrow? Or did you shoot the Spider Matriarch with an arrow and the arrow:
-did damage to her
-
and splintered into dozens of shards that did AoE damage
-
and caused bleeding for damage over time?
Because the latter is what firebolt currently does