I hate specialists with all my heart. These obnoxious loud-mouth heroes don't belong in Battlefield. Battlefield is not a hero shooter.
Hero shooter : A hero shooter is a subgenre of shooter games that cover both the first-person shooter and third-person shooter genres. These games emphasize hero-characters that have distinctive abilities and/or weapons that are specific to them.
Specialists specifically make Battlefield a hero shooter
Battlefield games previously were not hero shooters because previously our player character did not matter. Empty slate, no personality, no name. The appearance, background,
name, location did not matter with regards to that character.
In 2042 Maria Falck and Maria Falck only has access to the syringe gun.
In bf1 generic Ottoman, German, British, Red Army, White Army medic had access to the same stuff that the other faction's medic, who was a different face but still a generic no-name had.
In short, you could insert any character at all into any class and it wouldn't clash with the system but in 2042 retired Swedish(??) Combat Medic Maria Falck with defined backstory could never be anything but Maria Falck and her trait is specific to Maria Falck and Maria Falck only
As for functionality, it would seem classes are ironically more specialized than specialists.
Again using bf1:
Assault specialized in anti vehicle, SMGMedic specialized in healing/reviving, auto-loading rifle
Support specialized in LMGs, suppression, supplying
Recon specialized in snipers, spotting
Specialists are not special. Anybody can be anything and I find that extremely boring and lackluster