So, a lot of energy has been spent due to the obnoxious hyperbole of saying that a given class "sucks" because it doesn't do a thing one wants it to do, or is 5% under a "baseline" that isn't actually anything like a reasonable "baseline".
/snark
Why don't we, instead, talk about what would "fix" those classes for the people who have a bad experience with them?
Monk:
Runs out of ki too much? Give them +Wis mod ki at level 2, and let them regain wis mod ki once per day as an action or maybe regain wis+prof by spending 10 minutes in meditation.
Doesn't have enough "boom"? Let's workshop some extra things to do with ki, and some level 11 upgrades to Patient Defense and Flurry of Blows, to go with the level 9 upgrade to Unarmored Movement.
Patient Defense, at level 11, could upgrade to allowing a reaction attack when missed by a melee attack, or allow you to move as a reaction when you get hit while benefiting from Patient Defense?
Flurry of Blows, at level 11, could upgrade to add your proficiency bonus to all damage rolls with your Flurry of Blows.
Name Pending something something Thousand Stars, you spend a bonus action to add your proficiency bonus in damage to damage with thrown weapons, and double their range. You can make a single attack with a thrown weapon as part of using the ability. Also add to Martial Arts the ability to draw a weapon as part of every attack, regardless of number of attacks. At level 11, the benefits last until the end of your next turn.
Bond of The Earth, as a bonus action you enter a deeper state of balance within yourself. You add your Wisdom modifier to saves against charm or fear, and gain THP equal to your martial arts die +wisdom mod.
Senses of The Hunter, bonus action, you gain advantage on perception checks? Later you get darkvision or improve your darkvision? Maybe just "no disadvantage in dim light"?
Ranger:
The spells known are just too damn low, you guys. Give them known spells equal to half their ranger level rounded down plus their wisdom mod, and then add extra spells to Hunter and Beastmaster.
Not enough? Take all the replacements from the
Class Feature Variants UA and make them Enhancements.
Sorcerer:
Give them +Cha Sorcery points at level 3. Give them their Sorcery points at level 1. Give them spells known equal to half sorc level + cha. Let them replenish Cha mod sorcery points during a short rest. Give them an extra metamagic at each tier.
Also they should get signature spells that they cast for cheap or without a slot x/day, or something.
Warlock:
Give spells known equal to half level plus cha. Give third spell slot at level 5, 4th at 11, etc. Fold some of the invocation taxes into pact boons and into eachother. (eg, blade pact lets you get extra attack) Make the patron spells auto-known.