Basically the deal with kenku is that they're crow people cursed by their god for their greed and, as a result, they lost 3 things:
- Their wings and ability to fly, which they desperately want back Ok, that's easy to roleplay, gives them a option for a motivation hook, makes balancing them in a campaign easier than if they had wings.
- Their voices. That is, they have to speak using their innate ability to mimic any sound. What this means exactly is sort of muddy... the book mostly describes them using random sounds, words, and complete phrases to speak, but they still can read and write in normal languages. There aren't very many tips on how to actually pull this off aside from "when you're at the table don't just make noises and leave it to your fellow players to figure out what the crap your character is trying to say". By itself this is quite a roleplaying challenge.
- Their creativity. Yes, they lost any and all ability to be creative in any way. I find it rather ironic that they're right next to lizard men who are described at length as having an "alien minds" because of their strange emotional life, when kenku are apparently completely unable to, say, imagine a unicorn with 2 horns instead of 1 and draw it, like any 6 year old could do.
The book gives suggestions on how to roleplay this but fails to really grapple with the problem. It looks at them from the outside, describing them as followers, not leaders, that they can enact clever plans they hear but can't think of new ones, that they plagiarize everything. But the unlike the lizard men the book completely fails to help the reader understand their inner thoughts and limitations, and as a result it's really hard to imagine what it would be like to properly role play these guys. Without creativity just how much can they really understand language? We all know creativity itself frequently plagiarizes because there's only so many truly new ideas anyways, so are they actually incapable of mixing ideas with one another entirely to create a new one? To actually answer this question we need to open an entirely different book, the 5th edition monster manual, where says "Kenku cannot create new sentences", which implies that, yes, they are completely incapable of mixing, matching, and manipulating symbols.
But this seem inconsistent with their stated capabilities. It's said that Kenku can imitate coins in a purse to ask for money. But how did it learn to do that in the first place if it lacks the basic ability to manipulate symbols, the idea that "oh, that guy gets money in this situation, I should too, and I should communicate it by making money sounds, because that guy other there did it and that worked so maybe it will work for me!"
Which brings me to my point I guess: Overall, this description of kenku implies that they behave like a computer program. None of our computer programs can really invent anything new and we humans are vastly superior to them in terms of our ability to manipulate, mix, and match symbols, even if we are getting to the point where we can program an algorithm to write a pretty good piece of music. Even learning algorithms are forced to learn within our explicit parameters and can't learn new ones. So the kenku are not the cool sci-fi kind of program that has any kind of actual personhood, they're the uncool kind that tells your car how to not blow up and tells google to show you ads about cars, one that is insufficiently complex enough to appear human. Who the crap wants to roleplay that? Who the crap can roleplay that? I dunno. There's plenty of boring fantasy races out there but I've never seen one this weird without the authors adding giant warning buzzers in the text and suggesting that PCs really shouldn't touch it. None of the other races in the book were *this* bad.