I know how to do it but it's more work to account for 2 feats that are out of whack vs other feats.
Increase AC. Use the occasional poor lighting, slippery floors or invisible critters for disadvantage. Give monsters abilities like Parry (+ Prof to AC). Make them harder to hit. Done.
SS + GWM pay off is in DPR, with lower ACs bearing the brunt. Strip advantage, or increase AC, or impose disadvantage, and the feats become a liability.
SS also requires range to work, and both SS and GWM require the user to forgo a shield and have both hands occupied. Get up close and personal and beat them down, or hit them in a weak spot (like cruddy saves).
More work is not good design and even that Half an hour of prep is time spent that I would rather be doing something else either designing no combat stuff or messing around on the Xbox One or PS4.
No offence, but a lazy DM is a bad DM.
We had a saying the army 'Prior preparation and planning prevents piss poor performance'. It holds true to pretty much everything.
If you're struggling with Fighters doing more damage with power attack vs low AC's, God help you when high level spells come online. The planning to challenge a 'high damage fighter' is nothing compared to a well played high level mage with clairvoyance, scry and die, teleport, simulacrum, divination, wish, clone, planar travel and so forth.
High level / high damage fighers can be countered by increasing AC or HP, which is easily done on the fly, and if you get it wrong, you simply have a dead monster (of which there will always be more).
"Hey bro, I can deal 100 points of damage a round with my sword"
"Cool bro. I can teleport to another continent, scry your location, travel to other planes of existance, and call down meteors on your face while ethereal... or just get my Simulacrum here to do it while I chill in a planar dimension of my own creation"
Its no biggie. One of those situations can be reigned in by upping the monsters AC by 3 points leaving you all the PS4 time in the world. The other situation requires planning.