Reading this I almost gave into the urge to make a bet 
Of course there are things that you can do on Excel that you cannot do on Coda, such as:
- connect to Windows API (COM objects) through VBA
- play MIDI files
- interact with your filesystem, devices, drivers
- make a 3D shooter game on it (although I tried lol)
- manipulate doc schema (that’s a real bummer yeah; one of the reasons why I didn’t gave in. Although in many cases one could work around that with some smart schema design)
You have to do these with VBA though, which is an un-nice language to learn. Or hire $200+/hr consultants to code those for you without a slightest chance of you being able to maintain it yourself ¯_(ツ)_/¯
(it would be fair to say here that I’m myself a $200+/hr consultant on Coda, albeit I share a lot openly, and some more with patrons.)
@Brandt_Smith1 thanks for the shoutout!