It would be easy to just pop up in here and yell at you about why you're wrong, but I do understand what a person may feel when a game they like has changed completely and there's nothing you can do about it.
I've been in that boat. You force and force yourself to like this game, but something just feels off.
Personally I love the beta, but I do think it unfortunate and sad that you feel this way.
Then again you can't always make everyone happy.
However, there will be-and are-modes for purists like you.
I played Classic Slayer (team) and Covy Team Slayer the other day and it was pretty much classic Halo.
Only two loadouts for each with only 1 ability, sprint for Spartans and evade for elites.
The first loadout for Spartans and Elites were assault rifle and plasma repeater respectively and the second was DMR and Needle rifle. The elites had a plasma pistol as a sidearm while the Spartans had their magnum.
My memory kinda sucks and I'm not sure I was playing "Classic Slayer" with the Spartans, but at the very least I'd think these game modes are unchanged enough that you'd enjoy them.
If I remember correctly, Swat doesn't have any loadouts