It's a great game, but keep in mind I have no problem with complexity if it adds depth and more-or-less maintains setting logic. Not a fan of mastery properties either, but probably for different reasons than you.
One of the problems with Weapon Mastery in 2024 D&D is that only gives you one little perk.
Ryoko's Guide to the Yokai Realms for 5e has something like it, but it offers a perk or two at every tier of gameplay.
Light Mastery
For weapons with the Light Property, you get Lightweight or Multiweapon Fighting at tier 1.
Lightweight
Prerequisites: martial level 2, proficiency with at least one Light weapon. While the only weapons you are wielding are Light weapons and you aren’t wearing a shield or heavy armour, your speed increases by 10 feet .
Multi-Weapon Fighting
Prerequisites: martial level 2, proficiency with at least one Light weapon. When you engage in two-weapon fighting, you can add your ability modifier to the damage of the bonus action attack if the weapon is Light
By tier 2, you can perform a Superior Strike.
Superior Strike: Light
Prerequisites: martial level 6, a tier 1 Light advanced technique. You can perform a superior strike with any weapon that has the Light property
Tier 3 grants you Combination Strike or Reposte.
Combination Strike
Prerequisites: martial level 10, a tier 2 Light advanced technique.
When you take the Attack action and attack with a Light weapon, any attack roll you make as a bonus action this turn with a Light
weapon has advantage.
Riposte
Prerequisites: martial level 10, a tier 2 Light advanced technique. When you are wielding two Light weapons and a creature within your reach misses you with a melee weapon attack, you can use your reaction to make an attack against that creature with one of the weapons
And finally, Tier 4 with Light Mastery gets you Featherweight or Swift Striker.
Featherweight
Prerequisites: martial level 14, a tier 3 Light advanced technique. While the only weapons you are wielding are Light weapons and you aren’t wearing a shield or heavy armour, you gain a +1 bonus to AC and have advantage on Dexterity saving throws.
Swift Striker
Prerequisites: martial level 14, a tier 3 Light advanced technique. When you take the Attack action, if the only weapons you are wielding are Light weapons, you can make one additional attack with a Light weapon as a part of that action, but you do not add your ability modifier to the damage, unless that modifier is negative
All of the weapon types have these Advanced Weapon Mastery trees in Ryoko's Guide to the Yokai Realms. They're okay IMO, but kind of restrictive as they require you to use a specific weapon type in order to benefit from them. I prefer Level Up's
numerous Combat Traditions to them.