Not at all. The A10 is obsolete. The F15EX has a clearly important role to fill.
Simply put, you can't use 5th and 6th gen fighters for every mission. Too much maintenance, too much cost. There are a ton of non stealth required missions, and using an Fxx, NGAD, or F35 on those missions, is very wasteful. The F15 and F18 aren't exactly the easiest things to spot on radar anyways, at least not when they're trying to be sneaky.
A large field of stealths, down for repairs, because they were wasted on low level bombing runs, is silly.
And the F15 still has a few tricks up it's sleeve. Not only can it terrorize 99% of adversary fighters. It can fly 200' off the deck, below radar, at Mach Jesus, with nukes under its wings. It's no joke. If it's A2A missiles work, the F15EX is more than a match for Russian and Chinese fighters. Teamed up with a few invisible F35's, and it's a turkey shoot.
The game plan is tag teaming 4th, 5th, and 6th gen fighters, into an unstoppable force package.
An F35 can only carry so many missiles. But it can target enemy aircraft, and launch missiles from an F15EX that's on the other side of the Horizon (literally).
A dog fight isn't "beyond visual range" anymore. It's beyond, and way the heck over the horizon.
The F35 can launch missiles, from missile destroyers as well.
It's no secret that long range missiles are being brought into the game plan. An F18 flew with an SM6 SAM under its wing just a short while ago.
And an F15 going Mach 2+, without worrying about your RAM melting off, is still handy.