I love the setting of Brancalonia. I love the humor, I love the folklore, and I am currently learning Italian in evening classes to boot, so this is basically a perfect mix.
But I do not love that the authors picked D&D 5E as the rule system for this setting. Don't get me wrong, I find D&D 5E perfectly acceptable for heroic fantasy campaigns (and, in fact, I am running such a campaign right now). And I can understand this choice from a business perspective - it makes a lot of sense to tie your setting to the most popular RPG system out there.
However, Brancalonia PCs are not supposed to be great heroes, but fairly unimpressive never-do-wells. The rules deal with this by capping character level at 6, but I feel that this leaves the PCs with too little room to grow and removes much of the proper D&D experience. I'd rather use a rule system that was intended for weaker protagonists, rather than trying to distort D&D into something that is not.
So, what alternate system would you use for Brancalonia?
Gotta say I got the opposite feeling when I DMed it a while back. It's a clumsy system that badly needs a 2nd edition where they fix all the papercuts. I remember it being particularly unnecessary how the difficulty number has to be multiplied by 3 before you can use it. Just have the scale be from 3 to 30 to begin with so I don't have to remember what numbers are pre- and post-multiplication.
That said, it is somewhat easier to DM than 5e (which itself is heavily simplified compared to older systems).