The Stupification of 5e Monsters

I had a short thread about this on Twitter a while back, but I feel like I should put out some content in light of #blogtober (aside from my daily trick or treat Tweets) so let's talk about an interesting fact:

A lot of monsters got dumber in translation to 5th edition!

Exhibit A: The Mimic

I think I was reading through an issue of Rat Queens when I was caught off-guard by the thought of a talking mimic. I don't typically think about the intelligence of non-humanoid opponents my players might face I suppose. I was even more surprised to see this monster take such a big hit in the intelligence department: In 3.5 ed. the mimic's intelligence was a 10 and in 5th ed. it was cut exactly in half- ironically the mimic may now be unable to comprehend that math.

Exhibit B: The Otyugh 

I was vaguely aware that otyughs were intelligent. I think there was an adventure hook pitched by WotC back in the day that involved an adventuring party bargaining with one for information and that always stuck with me for some reason- probably because most of the players I've known would not think to engage in conversation with a quadrupedal trash monster with tooth tentacles. 

In the current edition of the game (compared to 3.5) the otyugh actually has the same intelligence score, but loses the ability to speak common and instead gets a limited telepathy to communicate simple ideas.

Exhibit C: The Roper

Possible SPOILER ALERT for an adventure that is both 18 years old and new again: If I were going to run the Forge of Fury, I would have probably cut the encounter with the roper. It is explained in the module that the creature is most likely too powerful to be dealt with by a party of 3rd level and that they should look to bargain with for passage instead. 

I don't have a copy of Tales From the Yawning Portal, but I don't think it is possible to parley with the creature now that it's intelligence score has dropped 5 points and it can no longer speak two languages. 

So what gives with all of this? Was an effort made to make the creatures more monstrous by making them less intelligent? Does this new design encourage more combat and less diplomacy with the non-humanoid antagonists? 

I feel sort of bad for them...