You'd be surprised how much better CPUs have gotten over the last five years. Even though the clocks might look roughly similar, overall performance has gone up

You'd be surprised how much better CPUs have gotten over the last five years. Even though the clocks might look roughly similar, overall performance has gone up by quite a bit. You probably only have 4 cores on a 2015 i7, too, and 8+ cores are standard now for high-end CPUs. Whether it'll make an immediate difference to you is game-dependent, but if you play a lot of AAA titles I'd definitely look to upgrade soon.