Isn't inspiration only usable on others?
Ah, yep, totally right.
There is nothing fair about this comparison, and nothing truly analytical about these arguments. It's all math without context and side-by-side lists of things we already knew, constrained to a set of premises that don't even make sense, as the primary assumption seems to be that each character exists in a vacuum.
If you put the simplest archetype of the simplest class in the game up against what is arguably the most complex class, of course you're going to end up with a lot fewer options and a lot less versatility. You also failed to comment on the huge differences in hit points and AC, which are not negligible. If you think the bard's healing makes up for that, fine, but then you have to factor in the opportunity cost of all those utility spells since you are spending so many spell slots to heal yourself, not to mention actions.
The main thrust of this post seems to be "High-level magic sure is powerful!" But I think you might want to actually play the high-level game with the classes in question before making such sweeping assertions as you have here. Real gameplay can uncover a lot of subtleties that simply will not show up in lists of numbers and class features.
You are exactly right. As I said at the start, the analysis is extremely biased. In the fighter's favor. Most days aren't going to run through 16 rounds, and they aren't going to let the PCs have 3 short rests. Most bards aren't going to rely on extremely inefficient direct damage spells like Dissonant Whisper. They're going to use things like Faerie Fire that boost the damage output of every single class, which provides a 37% damage increase
for the entire party for the entire combat. That's a single spell contributing as much damage to an encounter as the fighter does through the entire combat.
Song of Rest isn't something that applies to just the bard. If we had assumed that they didn't exist in a vacuum, but were together in a party of 5, Song of Rest would provide 52.5 points of healing a day, not just 10.5.
If we assume that the bard is throwing out her inspiration to the fighter and rogue during combat, it's providing a massive increase in the damage the party deals.
Now, huge difference in hp and AC? The fighter has a d10 hitdie. The bard's is d8. Gaining 1 extra hp per level is not what I would call "huge". The difference between a bard in Studded Leather and a Fighter in Full Plate with the Defense fighting style is...17 vs 19. Again, not quite dramatic enough to be what I'd call "huge".
And yes, real gameplay does reveal a lot of things. My own experiences at the table and reading through on my own are what inform me of these kinds of disparities. I think that "well you must have not played it" arguments have about as much credibility as Donanld Trump's demand to see Obama's birth certificate. It's an attack on whether someone is a "real" member of the community and a pointless distraction.
Real gameplay shows that the bard is really a fantastic support class that can be great at just about anything. And I honestly have no issue with that. The issue is that what the fighter gets--particularly what the fighter gets after level 5--quickly falls behind. Each level makes the fighter less effective relative to the threats the party might face and the scope of the stories that can be told. We were told that classes wouldn't have this problem, that the fighter--and by extension the rogue, monk, barbarian, etc--would be able to stand shoulder to shoulder with every other class, and this turned out to an empty promise. That's my view. I've shown my work, my thought process here. Bard gets this at X level, Fighter gets Y. I compare the two. My conclusion was that abilities like being able to summon down a firestorm or turn into a dragon or teleport around the world or create a clone of the fighter are all more impressive and more useful than getting a +1 bonus to your critical threat range.
You're free to disagree with me, but if you want to contribute, then show me how I'm wrong, rather than accusing me of somehow being a fake gamer.