I am a native Romanian and I can master more or less only English, French and Italian - while Spanish and Bulgarian are transparent to me: but German is not - nor Latin!
It seems to me obvious that the following is true: at least for a native speaker of any Romance language any other Romance language seems closer than Latin and much easier to master, in some cases very easy - like Toscan/Italian for a Romanian (maybe Napolitan would be even easier), maybe Spanish/Castilian for an Italian and Portuguese.
I was able to understand 80% of a spoken (standard) Italian communication at the TV very quickly after first exposed to it in my adolescence. Written text in French and Italian was rather easy to understand also, so learning these languages was easy (reading Montaigne and Leopardi is another matter).
Not to mention that English is also easy to learn - and in some cases other non-Latin languages may seem easier.
I am not talking about good grasp of the declination and conjugation and all other aspects that supposedly make Latin difficult, but mostly about understanding a body of written or spoken (descriptive, non-technical) text.
Is that impression misleading? - I mean: is it just because we don't hear people enough speaking and singing in Latin like they do in Spanish or French, because we are not exposed to Latin? (I remember having started in my childhood to understand Bulgarian after having been exposed by particular political circumstances more to Bulgarian than to Romanian television, just as later I've "started" to understand Italian and Spanish movies. - Would it have been the same for me with Latin if a Ciceronian-speaking TV had existed?)
If I would make a comparison with Darwinian evolution, where birds have evolved from reptiles, while all Romance languages are like birds, more or less similar to each other, Latin looks more like a crocodile than like a bird. I can explain why Bulgarian seemed familiar enough to me and English even more (Romanian has a lot of Slavic words, Bulgarian has borrowed some from Romanian, both languages share features of the so called Balkanische Sprachbund, and English is full of French and Latin words and has a simple grammar): but how come a Latin text is hardly more transparent to me than a German text?
If my impression isn't misleading, is that because all Romance languages have evolved from a common source (some stage/type of vulgar Latin, mostly unwritten)? Would that be closer to each of them than they are to each other?
And how could that have covered all the space from Portuguese to Romanian? Isn't vulgar/colloquial parlance always very local?
Have all these languages converged somehow and become similar by some rules of language development? Is it that they just have become simpler, reduced to more accessible common denominators?
What is the main reason?