I really, really can't believe nobody's mentioned the biggest elephant in the room yet: Modern English. It's quite a ramble, so I hope you could bear with me...it's just some frustration with the highly odd conlang I've been having.
Yes, the idea of adding layers of history to your conlang is cute, like you've done by conlanging it and then apply wholesale changes like the Great Vowel Shift and "spelling regularisations". The idea of introducing oceans of loanwords along the way to both augment the historical and sociological layers and mask any deficiencies potentially created is ingenious too. But let's all get past all that, shall we.
So let's talk phonology...this language has four (4) vowels in the close vicinity of low vowels, /æ/ /ɒ/ /ɐ/ /ɑː/, but
no low central /ä/. Great messing around, but that's typologically very unusual. They even have the audacity to make one major accent shift to /æ/→/ɛ̞/→/a/ like a) it could be a real thing, and b) the result would have been phonologically or typologically plausible or tenable, not to mention supposedly within a few decades. And they bend /æ/ in the other major accent in strange ways *away from* the low center (and raise /ɐ/ to a schwa) like some really enjoyable mental gymnastic.
So the author is working on multiple "major accents" because they'd like to show diversity. Cool thing. But to make the largest variety have syllabic r, l, and n's so that a sentence need not have any vowels is a tad bit too obvious in the imitation effort. 2/10.
Orthography - phonology - sociolinguistics. As said, it is perfectly fine to make your conlang all historical and messy, but it is completely unrealistic to then go on and say that "this language is the
lingua franca of the whole world". Like come on, that's hardly plausible. You wouldn't even get me or any number of fellow conlangers interested in learning it. What
makes you
possibly think that
everyone in the
whole conworld would be
seriously taking it as the
exclusive lingua franca?!!
Lexicon. For all the creative ways they have for asking questions, can't believe they've stipulated that *"how manieth" or *"whicheth" would be forbidden. 3/10.
Syntax. They want to make the language somewhat inflectional but not too much at all. Okay I get that. So they've put in minimal inflectional verbal endings just so that it is nominally a synthetic language even though also largely analytic. Not bad.
But how did they think they would be theoretically accounting for their so-called "phrasal verbs"? It's completely fine that verbal agreement is attached to the end of verb, and you can utilise prepositions to make new verbal constructions too, even idiosyncratic ones because idioms are legit after all. But what are the little "particle-ish things" supposed to be like in the so-called "phrasal verb"
carry out? The inflectional "ending" gets inserted in a completely messed up position. It's "We
carry out this investigation" but "we
carried out this investigation", not *"we
carry outed"? How's that supposed to fit in a scientific universal linguistic framework?
out isn't even a preposition according to their dictionary. Just arbitrarily wanting to flout language universals and syntactic structures isn't the way to work. Yet, they somehow make them extremely common in normal speech registers. 0/10.
Morphology.
- Word derivation: Um...I get they maybe want to be cute and subtly show the irony of the baked-in "subjugation" of this supposedly "dominant" people as contrasted to its (ridiculous, again) "high" status. But it is completely nonsensical and insensible to disable most any word derivation from native words, so that you can't regularly derive adjectives from common words at all and must resort to a different register and origin of vocab. Like the adjectival forms of bird, noun, nose, ear, and eyes don't become something like *birdish, *nounish, *nosish, *earish, *eyish , or *-ly, like their rules technically allow, but freaking avian, nominal, nasal, aural and ocular, and what's more, these "high register" loanword-based adjectival forms often have no corresponding nominal forms; i.e. the paradigm is defective in both ways just to be complementary, e.g. there's no form like *nase (even though there's nostril -- supposedly from the same loaned source but it just *has* to be different from the root form nas-; aura exists but it's even etymologically unconnected, whose adjectival form is the, right, auratic) -- seriously? What's the point of all this labor?
The hospital divisions for the stomach and the intestines, women's medical issues, and heart-related ones are the divisions of gastroenterology, gynecology, and cardiology, not divisions of stomach and the intestines, women, and heart (the words for "stomach and the intestines", "women", and "heart"). The long words are supposed to be double loanwords, borrowed from a different ancient prestige language via the "normal ancient prestige language", and originally mean "the study of ...". Apparently that's how biological words are supposed to work. How would they have the heart to make visiting hospitals and doctors so hellishly impossible for their conpeople? Have they no compassion or mercy? 
A cardiologist isn't a *heart medic or *heart (medical) doctor, but cardiologist. A psychiatrist isn't a *mind doctor, but psychiatrist, again a double loanword; the original meaning is supposed to be (romantically) "soul doctor", and here for strange reasons the creator actually makes a double loanword morpheme properly meaning "doctor", because "psychologist" now means properly "people studying psychology". But they don't use the morpheme practically anywhere else, e.g. it's never a *cardiatrist, and there's no *gyneciatry, as if it could suddenly make sense not to make the distinction here.
And while we're at it, there's no reason the adjectival form of bird should be avian instead of avial. It makes little sense to introduce so many derivational suffixes with the same meaning and quite arbitrarily stipulated rules of when and where they may or may not be applied.
- Hardly any compounding either. A hospital must be a hospital, a refined loan word originally meaning "of a guest", instead of the way more sensible *sickhouse or something. And patients have to be patient (loanword, originally "suffer-ing"; also homonym of the adjective for "patient") instead of like *sickfolk.
Creative, and clearly an insane amount of work and care must have been put in. But 0/10.
Just a few examples. Those interested are welcome to consult any grammar books published on the quite unusual conlang called "English".
