I’ve been doing the N4 series in standard (non-textbook-tied) order. I just noticed the example sentences for だんだん were suddenly much, much harder than they had been in previous grammar points. And when I say harder, I mean both in vocabulary (which I don’t mind), but also I think there were several not-yet-learned grammar points used.
Just me?
Every grammar point has many sentences. I think the sentences are random so you might get the difficult sentence right from the beginning instead of later.
Don’t worry about understanding everything. The sentence is just there to show you how the grammar point is supposed to be used. You don’t necessarily need to know all of it(there are probably Kanji that you don’t know as well).
It’s not just you. I remember that as well 
Thats probably Bunpros way of nudging you towards doing more reading right here
But while I do remember being frustrated at this back then, I cannot deny that it helped. In time, you’ll notice that you suddenly can piece together these sentences-- even if missing some vocabulary (well,.maybe its something like "he says that she thinks the time of something is important :)). But yes, right now it sucks a bit. Keep going!
I went back to Bunpro order after starting down the Minna no Nihongo route… I wanted to sequence in the simpler examples first. Yes, I have noticed this as well, but I’m grateful for it.
Oh I don’t think it’s bad, I already have to carefully pick through grammar when I’m reading, so I’m used to that. Just all throughout N5 and up to now in N4, I’ve been able to read the examples pretty easily, and there was no だんだん about how fast that all changed in one grammar point, ironically だんだん
I’ve seen ように enough in reading to kind of get it in context when I see it until i actually learn it here. But the 〜て〜て〜てる stacked verb phrases throw me. (and if you can’t read the verb, well, that’s kind of important 
)