I'm sorry in advance if this offends anyone, I'm going to be as polite sounding as I can. (Someone is guaranteed to be offended ._.)
1. "couldn't start with the weapon you wanted" <--- Not a fault. Puts EVERYONE on the same level at the start of a match. When everyone starts with the same weapons, the only thing that decides the outcome of a firefight is skill. When everyone starts with weapons they like, you're just giving good players a higher advantage. (I personally don't mind custom or forced loadouts)
2. Perks - Perks were an interesting addition, but if you aren't good at something like grenade throwing, an extra grenade isn't going to do much except create more opportunities to see where you are. In addition, if the person you are engaging is a better player, regardless of weapon or perks used, you are likely going to die whether you have helpful perks or not.
3. "I paid so I should be able to do this!" - You paid. You bought the game. You knew what you were buying, if you didn't, maybe you should do some research before the purchase.
4. "experience that works" "not having randomness" - That is your opinion, plenty of other people LOVED the predictability with forced loadouts, weapon spawns etc.
5. "gives too much power to experienced players" - Experienced players are usually going to have the advantage whether you have a power weapon or not, that is why they are called "experienced."
6. "lack of sprint" - In the Halo franchise, maps are scaled based on movement speed, you have sprint in a game, maps for 2v2/4v4 are going to be bigger than in games without sprint. Now, I can understand from a lore perspective why you would want sprint, but multiplayer shouldn't matter because the maps are designed to accommodate movement speed, whatever that speed is. Also, saying "why can't I run away from a fight I'm losing? why can the enemy player follow me at the same speed" is kind of dumb (I'm sorry but it is). If sprint is in the game, they are still going to be able to follow you at the same speed.
7. Aim down sights - This is not necessary, they are spartans, it says in the books that the weapon sights are linked to the helmets.
8. Going prone - I can kind of see why you'd want it, but it is an opinion. Going prone would only really be an advantage if you are sniping in a remote corner of a very large map. Other than that it would be used like it is in CoD (dropshotting, camping etc)
9. Cooking grenades - The grenades have rather short fuses, don't need to cook them. Pulse grenades (that I can remember) go off soon as they land. Plasma grenades stick to the target (doesn't help if you can't throw well).
Finally "wasn't interested in the multiplayer until reach, what does that tell you about the franchise" It tells us that you disliked the first 3 games, either because you weren't as good at them, or because you came to the franchise from a game like CoD where sprinting is a default, loadouts are basically all custom, and camping is the most used way to kill. (Once again, not trying to offend just saying)
1. "Bring the game into the modern experience" "who cares if it doesn't 'feel' like Halo" - The game is a modern experience ._. Adding prone and ADS isn't going to change that Halo is still a decently popular shooter. If a Halo game doesn't feel like a Halo game than why is it called Halo?
2. "The experience was broken" - That is an opinion, many now feel that way about the games you like (Reach and 4). Look at how popular Halo 3 was compared to them >.> (I like the lot of em anyways)
3. "cooking grenades, ADS, prone expected in modern fps" - I don't know why these are expected in every game in your opinion.. Is it because of CoD? Halo isn't your average FPS.. It's not based in modern times, it's futuristic. It doesn't need cooking grenades, the fuses are short enough. It doesn't need ADS, weapons are linked to the Spartans' helmets. Like I said above, I can see why some would want prone, but it's not necessary for a game like Halo where the weapon aiming doesn't need you to support the bigger weapons using the ground.
4. "Look at call of duty" - God, if I wasn't Mr. Nice Zag.... Anyways, CoD and Halo should NEVER be compared, they are two drastically different games. In the future don't compare them please. It causes unnecessary anger lol.
5. "I care about if it's going to make Halo an improved experience" - Once again, your opinion, many others will disagree with you there, others will agree. I'm one who disagrees, because all of your suggestions don't go with the canon of the games.
Most things in this spoiler I've already said something about ._.
Overall, most changes you are suggesting just don't fit the Halo franchise. They don't go with the canon (yes that is very important).
Tbh, loadouts make the game a heck of a lot more unbalanced than the forced loadouts do. They make it so that skilled players get to choose the weapons they are best with. You might think "Hey I have this weapon that I really like and seem to do well with," but when put up against a skilled player using their best weapon, all you're going to be getting is killed. Then the complaints start about a weapon being too good, someone cheating, etc etc etc. Forced loadouts start everyone with the same weapons, so (for the most part) everyone is on even ground. The only thing that determines who wins a firefight with forced loadouts is skill >.>
Sprint.. That's a difficult one to comment on.. 1. It somewhat sped up gameplay; 2. Enabled somewhat faster travel; 3. Uh.. That's about it XD
All in all, in the original post, you said that everything you were saying were FACTS. Fact - "a truth known by actual experience or observation; something known to be true" Opinion - "a personal view, attitude, or appraisal" EVERYTHING was opinion based in your post. Pretty much every argument about what should/shouldn't be added/changed is opinion based.
I don't know if you were making this because Halo 5 is going somewhat back to the older game styles or if you just hope that eventually some Halo game is made with all that stuff, but everything is an opinion.
Once again, I tried not to offend anyone (though I probably did).