Benjamin Olson
Hero
Well all spells are "situational". It's really a matter of how often the situation they are for comes up in your game. A "situational" spell for a situation that comes up regularly is a good spell.
It seems like you design encounters around CRs, and yeah Fireball doesn't shine for very long there. I design important set-piece encounters with CR in mind, but the packs of goblins, kobolds, zombies, bandits, orcs, town guards, and commoners don't disappear from my world or stop doing their things just because the players have leveled past them. They continue existing wherever it makes sense for them to exist, and while I'm not going to plan a lot of big encounters around them (except the occasional, post level-up "steamroll these mooks to feel awesome" encounter), if it makes sense that the enemy the players actually need to fight has a lair swarming with mooks of a particular ilk then said lair will swarm with mooks of said ilk, and players have ways of creating their own encounters anyway. Which is all to say that tables that take a more simulationist approach, where the world doesn't change CR to match the players, will continue to have Fireball and other high quality low level spells have more continued relevance, whereas tables that are more gamist, where players leveling up causes every creature they encounter to have also levelled up, aren't going to have nearly as much use for such things.
Fireball is a good spell at most tables I've run or played at. It does an above average amount of damage for its spell slot in a relatively easy to position area of effect. It's main flaw is not living up to its reputation, because nothing possibly could.
