AbdulAlhazred
Legend
The first quote point of view is using monsters straight from the monsters manual without changing them.
The second quote point of view is using the monster creator to alter the level of the monsters.
My way of doing it is a way between, very similar to 5e. HP/damage output scales depending on the level of the monster, while to-hit/defences remain relatively static relative to the players.
I have had encounters with hordes of low level mobs in 4e as well, and they were really boring. I played a Wizard who had gone for great AoE damage and just slaughtered them. They could barely hit us, and we could barely miss. I much prefer 5e's way of doing that, where a low level mob has a good chance of hitting you, but the damage might only be half of the normal. I have also been in encounters with mobs 5 levels higher, and the characters really do miss a lot. Sure the encounter went ok, but it's really boring when the PC's keep on missing. I just resorted to auto-damage attacks of assorted forms (Flaming Sphere and Magic Missile). The characters without such abilities kept on missing. Pretty boring for them.
Reskinning is super easy in 4e, since the 'core' aspects of a monster are pretty much defined by level, role, and type (minion/regular/elite/solo) and the specific mechanics of any given power/attack can be quickly reskinned its not really a huge challenge to add whatever elements you need. For instance I needed a race of half-ghostly ancient shape-shifting shadow creatures. The boss was a reskinned white dragon, the other major bad guys were reskinned NPCs stolen from here and there, the majority of the bad guys were reskinned Jackalweres and werewolves. I wrote up a monster theme to apply to all of them so they had a couple of fairly consistent abilities, but the end result was great. The 'white dragon' boss was awesome, his bite was a giant axe, his claws were claws, and his breath was an unearthly howl.
Its quite possible to build slogs and walk-overs in 4e if you don't pay careful attention. 4e can really reward good DMing, but it can also punish DMs. Any system will fall flat now and then. I think 4e is actually one of those systems that is easy to learn, but not so easy to really master. I learned a lot from running it, our games were all pretty successful, but there were definitely encounters that didn't pan out and the odd klunker skill challenge. I really do yearn for a more polished and perfected 4e!