In my comments, I did not focus on class balance. Some things that I mentioned include the following:
1. Barbarian:
a. more subclasses and options for for non-mystical raging warriors
2. Bard
a. Either move the subclass to first level or create a Level 1: Martial variant that receives the armor and weapon proficiencies of the valor bard and then adjust the Valor Bard as necessary.
3. Cleric:
a. Add level 1 choice similar to the Warlock's Pacts- something Maybe call it Order. Possible orders could repreent Monastic/Cloistered priests (more scholarly order, no armor, simple weapons, extra skills), Mendicant (beggar order with no armor. Perhaps give them martial arts to defend themselves), Itinerant ( a more worldly travelling order), and Templar (Martial order with heavier armor and martial weapons) . Move Armor, Weapons, Divine Strike, Potent caster to Order.
b. limit clerics to a smaller shared list for all clerics with spells (e.g. augury, bless, bestow curse, remove curse, planar ally) and spells from the cleric's domain. Possibly add third smaller list based on alignment.
4. Druid
Unlike most people, the only Circle that I think is close to my liking in implementation is the Circle of the Land. However, if the Druid is going to be the class that, officially, handles "Shamans" through subclasses, both the Circle of the Land and the Circle of the Shephard both fall short for my tastes
a. Circle of the Land can be for Shaman's dealing with Spirits of Place, the Circle of the Shephard appears to be dealing Totems, and we need one dealing with Ancestors (parent, sibling, grandparent).
b. The druid "shamanic" subclasses should be able to Command/Turn spirits and non-corporeal undead similar to the cleric's turn undead as Shaman's will bribe, persuade, cajole, and intimidate spirits
c. The "shamanic" druid subclasses" should be able to use the Spirit for guidance or scouting on a short rest without using a spell. In many cultures, a spirit associated with the Shaman (and not bound to a specific location) can be sent out to seek out additional knowledge about nature, healing, etc. from other spirits when both the shaman and their associated spirit does have knowledge on a given topic.
d. I find the Circle of the Shepard especially annoying beginning with reading and writing sylvan (and I dislike similar abilities of other subclasses). Second, i want more generic spirit abilities or more spirit examples. Depending upon culture or environment the same animal can be associated with different characteristics or abilities or a different animals associated with a specific characteristic.
5. Fighter
a. Move the fighter subclass to first level or create a Light Fighter Variant option at Level 1. In addition to the Musketeers, in at least one version of both Zorro and the Count of Monte Cristo, were trained as warrior with battlemaster type maneuvers with Zorro having the Criminal background and Edmound later multiclassing to Rogue (Mastermind?). This is also useful for groups that do not use feats or multiclassing.
b. more archetypes based on real world cultures, legends, and myth.
6. Monk
a. split the class into two classes or create a broader Martial Artist class with monk being a subclass. Currently, every concept with unarmed fighting and ki (or some similar ability) seems to gets lumped in a subclass even when many of the base class abilities don't fit the archetype.
b. a first level Iron Monk variant based on Strength/Con and representative of more Hard styles
c. allow for more player choice and customization of martial arts styles.
7. Paladin: provide a non-spellcasting (or lesser spellcasting version) variant similar to Holy Warrior variant from the 3e Complete Champion
8. Ranger: provide a non-spellcasting (or lesser spellcasting version) variant similar to Champion of the Wild variant from the Complete Champion
9. Rogue
Not all rogues are thieves and this create an awkward transition for those multiclassing into the Scout and Swashbuckler
a. add a Level 1: Wilderness Rogue variant at Level 1 to bridge. This would provide a few skills swaps, replaement for thieves tools with an outdoor related kit, and an optional variant for Thieves' Cant (perhaps Signals and Trail Signs).
b. Level 1: provide an options for educated and scholarly rogues with no affiliation to a thieves guild. Options would include a variant to swap Thieves Guild with an extra language, optional skill swaps, and options that replace thieves tools with another tool or kit.
c. variants that replace Elusive, Slippery Mind
10. Sorcerer
1. Provide an Arcane Heritage for those coming from a lineage of sorcerers or otherwise have a natural inborn talent for magic (e.g. Sabrina and Tabitha from Bewitched, Merlin from BBCs Merlin)
2. Provide a Fey Heritage
3. Provide an Abyssal Fiend Heritage
4. Provide an Infernal Fiend Heritage (e.g. Damien in the Omen, both Damien Hellstrom (Son of Satan) and Satana from Marvel Comics)
11. Warlock: if it has not been done, Patrons for each of the Arch-Devils and Demon Princes with unique abilities appropriate to the Demon or Devil in question.
12. Wizard: Go back to 2e Tome of Magic and PO: Spells and Magic and convert the remaining Effect Specialists and Thaumaturgical Wizards.