To fireball or not to fireball?

Please help me resolve some worries, and problems i have. I am a relarively newish player, started to play in october last year, and i have a little wizard who just hit lvl 5. My party was like "yeeeaaah, firebaaaaalll", and i was like "there is no way i am picking fireball", insert surprised pikachu face. From everyone i told. I am very aware what fireball is capable of and am very reluctant to use it because of it. Our DM loves his dungeons, that means smaller and bigger rooms after long thin corridors, usually 1-2 characters wide. My party and dm urged me to pick fireball regalrdless, because it is such an op spell, i wanted to chose something niftyer but relented and chose damage, but i don't have it prepared because it takes away space from (in my opinion) more usefull spells. My party keep telling me i should use it because i usually roll high on initiative (i roll average, they just remember a few nat20s i had), but the reality is, that we have a marching order of the big guys walking first and i tiptoe further behind, so if they run into danger around a corner, i usually dont have a line of sight on any targets, even if i roll high on initiative. This means the enemy is usually right on top of my friends. Even in a bigger room, our frontliners are way too close, and the rooms are not big enough, so i would just nuke my whole party. They even told me not to worry if they got hit by it, but i am really unwilling to give tem friendly fire on top of the damage they already are getting from enemies. What could i do about this situation? My party members have years and years of experience and i keep thinking they must be right, but i never used fireball once regardles.

(Sorry for the mobile text wall)