Over compression in modern metal production!! Kills all the dynamics in the loud and soft sections of the songs leaving records that sound dull and lifeless. End the goddamn loudness wars already!
Also, programmed drums. All the typewriter click drumming shit can fuck right off. I don't care that they're not perfectly synched or that the double bass doesn't have that perfect even sound. Smooth it out a bit, but don't take the human factor completely out of the game. You absolutely can't replace the feel and swagger of the human machine, especially in a live setting. Science has my back here:
https://www.mic.com/articles/113504/science-shows-why-drum-machines-will-never-replace-live-drummersMan, missing the live shows real bad. Fucking die off already, Covid-19.