Have you actually used it much?
That's the beautiful thing about math and game design: I don't have to use it much to be able to see what it is capable of. You can do a series of calculations and get average values.
People are assuming 65% hit chances and 65% saving fails not taking friendly fire and fire resistance into account.
1) While fire resistance is plentiful in the MM, it's not actually that plentiful in most games or adventures. (57 out of the 163 Fire resistant and immune enemies are demons or devils, for example, and unless you're adventuring in Hell you're probably not fighting many of those, and that's not counting "Abyssal Chicken" type monsters, just the 'important' ones)
2) Friendly Fire is a situational penalty that can be erased with 1 sorcery point. And even if you choose not to spend it, it doesn't negate the damage output of the spell, which is the point of comparison.
3) 65% hit chance is pretty decent. It's not insanely good or anything, but it's a reasonable baseline to work off of. Is it possible to get another +4 to attack? Sure. Bardic Inspiration, for example, or rolling well on Bless. But most of those benefits apply to one attack or require you to roll to see how much benefit you get on each attack, making them swingy.
And while you'd be cool applying Bardic Inspiration or Advantage to all attacks against all targets of
Chromatic Orb if the first one has Advantage or Bardic Inspiration... I sure as hell wouldn't.
Personally I tend to avoid fire and poison damage. At least to build around.
Fair. That's your prerogative. Personally I make a monoclass character with minimal, or zero, feats and don't bother breaking out the spreadsheets to try and figure out the most optimal build, instead coming up with a concept and running with it, even if it's suboptimal. We all do things our own ways.
It's trivial to buff accuracy up around 85% or higher.
Hitting allies in an AoE they know I intend to use on my first turn is just as trivial. They decided to get into the blast radius and can make their saves like everyone else!
Of course the rounds spent gaining the 85% buff and the rounds spent Healing the party balance out, right?
Vs high AC opponents ill switch to a save or suck vs CO.
Personally I like stuff with half damage failstates rather than save or suck. They're more fun for everyone involved.
No one likes getting locked out of combat because they keep rolling crappy saves, after all. Even the Narrator.
Other interesting thing is does it open up a close enough equivalent to acid/frost.
S'truth. Of course you could also talk to your DM about trading out the Fire for Acid Damage during downtime as a "Research" thing to change the spell's damage type always. Then you're only looking at 62 Immune/Resistant enemies (well, that -was- 5 years ago, now, there might be more at this point). Though that'll depend on your DM and adventure.