MCDM, Matt Coleville’s company, just released Flee Mortals! This 400 page book includes new takes on existing 5e monsters and a few brand new ones – all in MCDMs style of cool tactics and action-oriented designs. I had the great pleasure of designing the vampires in this book including the monstrous Count Rhodar Von Glaur!
Check it out!
If this is how you feel, pick up all the kobald press monster books. Between Tome of Beasts 1-3 and the creature codex, that’s probably more monsters than WotC have printed across all of 5e.
Also check out the Monsterous Menagerie be Level Up 5e, this book can take a few extra liberties as it’s for EN Publishing’s take in 5e, and that difference means they can really make interesting monsters that are basically compatible with standard 5e.
I’m also a fan of the Grimhollow Monster Grimoure, although it’s probably the closest to current 5e content, and is only elevated by it’s consistent dark fantasy tome, sort of like the monster from Van Richens Guide to Ravenloft.
There are probably 1500 monsters across all of there which are all more interesting than many WotC monsters, I couldn’t recommend them enough.