You do realize that nothing in 4e precludes you from using monsters as NPCs and giving them complex motivations, and nothing in 3e or previous editions enables this more than 4e. Roleplaying and using monsters creatively is entirely a DM issue, and has to do with how the DM wants to run his game, and what NPCs and story elements would make for a more engaging campaign; its NOT a rules-specific sort of thing.
For example, last session, the PCs managed to trick/impress a large warband of hobgoblins into helping them attack the keep of a corrupt order of Baphoment-worshipping knights. After scouting the keep, the PCs realized they were in WAY over their heads for a direct fight- I had anticipated they would try to sneak in and try to recover a holy relic the knights had taken. Instead, the PCs approached a nearby warband of hobgoblins as worshippers of Bane (in order to avoid an initial fight with the hobs), and asked for their help in eliminating a group of knights that were corrupted by Baphomet. In order for the PCs to accomplish this, they had to overcome the hob's suspicions, and prove themselves. We set it up as a long roleplaying and combat skill challenge, involving a 1-on-1 duel with a hob champion (the PC lost, but still impressed them), negotiaions with the shaman and warband leader for their aid, and trying to convince the shaman they were actually followers of Bane (this one was tough, but the PC cleric managed to use what he knew of Bane well enough to pass it). The warband leader actually developed a deep respect and admiration for the PC fighter during their duel, and the two have struck up a friendship- unexpected, but the hobs could be highly useful allies in the future. The shaman doesn't trust them, but the prospect of looting the keep for its forbidden and arcane secrets is allaying his doubts for now. The MM doesn't say any of this, but I came up with something that made sense for my world and campaign, and have a deeper and richer world for it.
Likewise, claims that 4e doesn't support roleplaying are completely bogus- the assertion that it is impossible to roleplay in 4e is entirely a failing of the DM and players. 1e and 2e didn't have skills, proficiencies, or feats for roleplaying, yet I recall roleplaying some deep character-driven campaigns using those systems, just as I am using 4e now. All versions of D&D have emphasized combat over all other aspects of the game, but 3e cluttered roleplaying up with feats and skills, and too many times over the years I played 3e I saw people reduce roleplaying to a die roll. I will admit the one failing 4e has in this category right now is that there are not many powers/rituals that were spells in previous editions that could be used more in RP situations, but thats a minor quibble- either wait for expansion books to come out, or write up your own powers/rituals to fill in the gaps (as I did). The onus of roleplaying lies with the DM and players, and if they are incapable of roleplaying, the system doesn't matter.
As for the "unfun" thing, I've not seen anything anywhere in 4e that said this. If anything, 4e says "do whatever you want, its your game."