This reads like the problems you point out are all exclusive to wizard, that is wrong.
I
literally said that every other spellcaster is also unbalanced, just to a lesser degree than Wizard: "some of
them aren't especially great for balance either." Further, I didn't even say that Bard
was balanced, just that it was
closest. That cannot be true if one thinks that Wizard is the only class with problems. And, per my previous
email post, I expressly said that the problem lies with Vancian spellcasting, and Wizard is simply the class that actively avoids
any of the tools one might use to fix the faults of Vancian spellcasting.
The most important thing a wizard can do iin combat its debuff & engage in battlefield control of monsters in ways that mitigate & reduce resource (hp spell slot charges etc) attrition or buff their allies to make those allies so they do that by operating more effectively with greater safety.
I disagree. There are numerous situations where the Wizard does not simply
enable others to finish the job--where they can single-handedly defeat most or even all of an encounter with the right choice of 1-2 spells. Once you get past the very earliest levels, spending 1-2 spells on an encounter is a perfectly normal cost for the Wizard. Even if you somehow manage to
actually reach 6-8 encounters a day, despite that being stupidly over-long compared to what most players are actually interested in doing and most DMs are actually desiring to run, that's still ~9-12 spells a day, something the Wizard can
always achieve by level 7 counting Arcane Recovery (or 9 without it.)
This isn't unfixable. There are ways to address it. The problem lies with folks who refuse to permit the possibility of a Wizard that isn't omni-flexible, totally focused on Spells And Only Spells, and generally having
the most powerful and diverse selection of spells in the game with the ability to eventually have Cleric-like spellcasting with a lenient DM (once you learn all the worthwhile spells of a given level, you have effectively paid money, otherwise mostly worthless for a Wizard, to get the Cleric "you can memorize any spell on your list" feature.)
That has always been the case but resource attrition was downplayed so much there is very little value added by reducing it & PCs operate so effectively with such a dense layer of near plot armored levels of safety there is not much value in increasing that even further.
The problem is, you need something that
consistently provides a stick, not just a carrot, for spellcasters who blow their load ASAP. 5e simply does not have a mechanic that can do this, so the DM is forced to use fiat and framing, and repetitious uses of the same forms of fiat and framing gets old really fast. This encourages the development of a DM/player arms race, where caster players look for ways to maximize their ability to reject "soft" restrictions and leverage the social contract to oppose "hard" restrictions, while DMs must escalate to ever-greater threats and ever-sharper demands in order to push things back toward equilibrium.
And, of course, the usual proposal for how to introduce this "the mechanics need a stick" thing is to make spellcasting
horrifically awful, e.g. "madness" mechanics or "casting spells can literally just straight-up kill you every single time," which is simply not going to fly with the average consumer. Such brutal "survival game" mechanics are
great for niche settings/campaign concepts or opt-in game modes, but cannot and will not work for everyday players, especially not in this brave new post-podcast world where many new D&D players come to it wanting something closer to a serialized narrative and not at all like a "mercenary company" where the
brand is more important than the
people.
Then After the rest of the game shifted to move from a team game to a group that solos near each other in ways that kicked the wizard's niche out from the "important contribution" bit of d&d's venn diagram the knowledge skills were altered to meet the needs of the do everything great yourself main characters. That was an important part of what the wizard brought to the table before though. Even without knowing how it worked mechanically it's easy to see
when laid out & has already been mentioned in the last few pages.
I have been explicit in my criticism of 3e for a very, very long time at this point, saying almost exactly what you've said here. On another forum, I phrased it as, "4-6 solo adventurers who happen to adventure in the same place at the same time." This was very specifically why I had such issues with 5e's design during the Next Playtest. I explicitly and repeatedly called this out as a likely problem, and was almost universally dismissed.
Being Cassandra is not fun.