While I think 5e on the whole is a lot better than 4e, it is somewhat lacking in the monster department. There are three main things I think 4e did better with monsters:
1. Ramping up humanoids. In 5e, pretty much every natural humanoid monster is an appropriate monster for 1st level characters to fight. Bugbears, duergar, and thri-kreen top the humanoid pecking order at CR 1, and below those we have gnolls, svirfneblin, hobgoblins, lizardfolk, orcs, and sahuagin at CR 1/2, bullywugs, drow, goblins, grimlocks, kuo-toa, and troglodytes at 1/4, and kobolds and merfolk at 1/8. The only ones going beyond that are gith, lycanthropes, and quaggoths. In 4e, you had a progression of humanoids starting with kobolds and goblins at level 1-2, then moving up to orcs and hobgoblins at level 3-4, bugbears, gnolls, and lizardfolk at level 5-6, and shadar-kai and troglodytes at level 6-8. Sure, 4e had a different level scale than 5e does, but it would have been nice to have the humanoids spread out a big more over CR 1/4 to 5.
2. Variety in monsters. 4e usually provided multiple variants of a particular monster. In some cases it was just a higher-level version of the same thing (Iron Gorgon and Storm Gorgon), but (particularly among humanoids) often they were differently "classed" monsters - e.g. goblin blackblade for the sneaky ones that stab you in the back, goblin warrior for the relatively straight-forward fighters/skirmishers, goblin sharpshooter for the archers, and goblin hexer for the magical support. Volo's Guide to Monsters helps out with this a little, but nowhere near enough.
3. Monsters that do cool stuff. A lot of 5e monsters are just big bags of hit points and damage. By comparison, most monsters in 4e at least had a little something extra - and in 13th age, almost all the monsters have something cool to do. Perhaps one does not need to go that far, but it would be cool with monsters with more abilities.
1. Ramping up humanoids. In 5e, pretty much every natural humanoid monster is an appropriate monster for 1st level characters to fight. Bugbears, duergar, and thri-kreen top the humanoid pecking order at CR 1, and below those we have gnolls, svirfneblin, hobgoblins, lizardfolk, orcs, and sahuagin at CR 1/2, bullywugs, drow, goblins, grimlocks, kuo-toa, and troglodytes at 1/4, and kobolds and merfolk at 1/8. The only ones going beyond that are gith, lycanthropes, and quaggoths. In 4e, you had a progression of humanoids starting with kobolds and goblins at level 1-2, then moving up to orcs and hobgoblins at level 3-4, bugbears, gnolls, and lizardfolk at level 5-6, and shadar-kai and troglodytes at level 6-8. Sure, 4e had a different level scale than 5e does, but it would have been nice to have the humanoids spread out a big more over CR 1/4 to 5.
2. Variety in monsters. 4e usually provided multiple variants of a particular monster. In some cases it was just a higher-level version of the same thing (Iron Gorgon and Storm Gorgon), but (particularly among humanoids) often they were differently "classed" monsters - e.g. goblin blackblade for the sneaky ones that stab you in the back, goblin warrior for the relatively straight-forward fighters/skirmishers, goblin sharpshooter for the archers, and goblin hexer for the magical support. Volo's Guide to Monsters helps out with this a little, but nowhere near enough.
3. Monsters that do cool stuff. A lot of 5e monsters are just big bags of hit points and damage. By comparison, most monsters in 4e at least had a little something extra - and in 13th age, almost all the monsters have something cool to do. Perhaps one does not need to go that far, but it would be cool with monsters with more abilities.