SPOILER long post incoming. Because to answer to this topic we have to cover few things.
The FPS military game approach during the 2000's :
Rude, organic, feel at war, immersion. Hell look even COD at the beginning (World at War, such a great one)
Time go by, some games start to make FPS less "military" and more quick fun easy cool shooter. BUT, Battlefield decide to keep this approach of :
You're a soldier. War immersion. Organized and paced gameplay, structured. It was this sweet spot between COD and ARMA
==> to do so, some key points will define what is BF. :
- the player character behave like a human
- infantry is supported by vehicles
- you are (have) not a personality, you are a soldier, among a squad.
- you are given a class, you have a ROLE among your squad. Your appearance reflect your role
- you have a squad leader & commander, you're on a battlefield with a specific objective
- interactive environment (through destruction)
- mode HARDCORE if you want to push immersion further, you have to be even more careful and rely even more on your teammate.
Now player will always play the way they want within the margin they are given. But this was the structure, the core of the gameplay. The BF DNA. And it was by consequences attracting a certain type of player.
Let's see 2042.
(we saw this direction start to appear before, BFV been quite a signal)
- player run and move at a superhuman speed, jump and climb in 0.5s some 2m tall object and fences
- vehicles are not here to escort infantry, but are fun things on their own, in mass quantity. Can even pop out anywhere (hell, even roof)
- you have a face, a personality, you are not a soldier with a role you are a hero with tricks. You have cool looking outfit that doesn't reflect what you can do, but make you "unique".
- you can do and be whatever you want with whatever combinaison you want, no matter your "character"
- you have a leader on the paper but he can't do anything you can't
- environment is half interactive (mostly due to map design)
- no more mode HARDCORE
It's a simple key point comparaison. Between what along opus defined BF DNA, what's left in 2042.
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Now we are not lacking of games nowadays, the simple no class cool quick hero trendy individualist shooters are countless. But, we still had this sweet spot that was BF. This slightly more serious and rude game. Pretty much the only one of his genre done by a AAA studio.
EA came back with a marketing that was saying out loud "the real BF is back" : people expected a game that smell in everyway the BF DNA.
People discovered that pretty much none of the DNA was there. The disappearance of the class to replace them by heros being one of the most obvious change ... well it was the cherry on the icing, the greatest beautiful final middle finger from EA to the BF fans.
Classes core idea was aligned with the core design of BF. To give you a role as a soldier, to structure things. While specialist (and not only through their outfit and cheesy lines), by the hero approach instead of soldier, the zero restriction (create your own recipe) etc ... diluted the notion of role and promoted the individualist style. Removing all the structure and organization. Wiped by the super dude that can do everything.
Which goes among with the messy unorganized gameplay that 2042 suffer from. Heros clones flying jumping around with "tricks". No idea who does what. Vehicle absolutely everywhere passing by at 300 km/h.
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Consequences, so many people say specialist doesn't belong to BF. And it's not subjective approach, it's remarks based on BF DNA.
Now one could say, it's evolution, games change over years, so do BF. But evolution doesn't means turning your back on your own licence to attract a completely different customer target. Which is obviously what EA tried. And i emphasis the "tried" because number speak for themselves, it's a failure. Indeed Specialist is not the only source of it, but it's a whole. The specialist concept is a huge part of the problem linked to this new approach of the gameplay that do not fit a BF.
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So i'll turn around the question. What good does the specialist bring in a BATTLEFIELD game. And i don't count the more free weapon choice as argument, this simple change could have been easily done with classes adjustment.
Like allowing all classes to pick an Assault Riffle if they wanted. While giving each of them one kind of weapon specific to their role.
And some of the cool specialist tricks ideas as primary gadget choice (let's remember specialist are in fact gadget slot 1)