The F-15 was lowered to 12.7 despite it’s strengths because those very same strengths do not influence the game in the current 13.0-14.0 meta.
To vastly oversimplify, it’s strengths are 4 very good IR missiles, and competitive flight performance. Not exceptional flight performance, you’ll still handily lose to F-16s or Gripens, and some of the more nimble fighters can cause problems if you misplay. Also boat loads of countermeasures, but this is a passive advantage.
Meanwhile, it’s disadvantages are a crippling weakness in BVR/head on engagements due to it’s poor RADAR and unreilable AIM-7Ms.
On the whole, this might sound like a fairly balanced list. But due to how most 13.0+ games play out, it really isn’t. The outcome of the game is almost always decided by that initial ARH salvo of missiles. It really shouldn’t be, even Fakours aren’t difficult to dodge by just pulling into a notch, but I’ve consistently watched half of a team eat easily dodged missiles and die, leaving the other half to be easily cleaned up by the other team in a series of dogpiles.
To be fair, the F-15s are far from unique when it comes to struggling with this. All other ~13.0 aircraft are in a broadly similar boat. But at least they have advantages that help mitigate this lack of impact early in the game.
They either have ARHs themselves, ERs which are credibly dangerous SARHs even against ARHs (Depending on the circumstances of launch), an AESA RADAR to make the AIM-7Ms a bit more credible at range (alongside one of the best dogfighting flight models in the game), or, at worst, are more agile and with a greater number of IRCCM missiles so they can do more if they do manage to close the distance (M4K, Gripen).
Basically, what it comes down to is that if the F-15 can get into a dominant position, it can be very strong. But it completely lacks the ability to influence the early game to ensure it does
If/when the ARH meta gets rightly shoved upwards at least a couple of BR ticks, then the F-15s can go back up. But right now, it seems there are far larger fish to fry. The only planes that should have ARHs at this tier should be bricks that sacrifice everything for carrying a couple of ARHs. The fact that there’s only 0.3 BR between stuff like the ICE and Tornado F3 Late and the premium SU-30s is hysterical.