Last Best Hope paints Andoria, Earth, Tellar and Vulcan as the Big Four. Apparently, Alphacent isn't a founding member in this continuity?
I mean, canonically, Alpha Centauri has never been established as a founding member. ENT's "Zero Hour" talked about the founders, but it framed them in terms of species rather than in terms of planet or planetary state: "Humans, Vulcans, Andorians, and Tellarites." Which left the door open for the Litverse to establish Alpha Centauri as a Human-populated fifth founding state. DIS's "Will You Take My Hand?" had scenic art that implied founding roles for Earth, Vulcan, Andor, and Tellar through the use of their respective emblems at the Federation facility we saw in that episode, but it didn't use any art to imply a role for any other Member State, including Alpha Centauri.
As Christopher noted, though, there's probably still room for us to imagine that the Alpha Centauri Concordium was a founding member if we presume it's been largely eclipsed in political importance since then.
Also, Mars is devastated in PIC. That's a major thing to happen to a coreworld - unless the new continuity only treats Mars as a colony instead of a Federation member in its own right.
Well, the canon has never established Mars as its own separate Member State. The Litverse has, but the Litverse has also always implied that the Confederated Martian Colonies has always had less power and influence than Earth and has resented its second-tier status. The
Romulan War duology referred to it as the "cosmic Canada." (The Litverse has
also never been able to settle on a single name for the Martian legislature --
Beneath the Raptor's Wing referred to it both as the Governing Council and the Assembly, while
Section 31: Control referred to it as the Martian Parliament.)
This
is consistent with how Mars is portrayed in PIC, actually; the entire planetary surface looks to have been devastated, but there were only around 92,000 deaths. If Mars had achieved a level of power and influence within the Federation on par with that of Earth or Vulcan, we would expect a population somewhere near 5-10 billion. I would hypothesize that Mars probably has a much larger population underground and/or in domes that managed to escape destruction, but its population has probably always lagged behind the Earth/Vulcan level.
The attack on Mars was a pretty psychologically devastating thing for the entire Federation even
if Mars were only an Earth colony, though -- an entire planetary surface got bombed deep within one of the Federation's core systems. If someone managed to blow up Liberty Island but wasn't able to touch Manhattan, that would still be a major psychological blow, after all.