Please improve the spaced repetition. It's basically too simplistic and broken.
It seems to me that the logic of Duolingo is to separately decide what topic you need to practice and then decide what words are weak in that topic. This means that for example every now and again Basics 1 comes up and I have to go through "Yo como", "No, nada", etc another time, which is actually a complete waste of time.
There seems to be no recognition that these basics get reinforced by basically everything else you do.
And nevermind the absurdity of my or your elephant drinking milk as any kind of useful communication.
Duolingo should have the ability to figure out what words are weak and then, from that, work out what topics you should practice, not the other way around.
And honestly for things like Basic 1 and other stuff at the top of the tree, I'd be pretty happy if I could just turn off those entirely at this point or, better yet, have the system reach a point where you never have to go through them again.
The peculiar sentences you come across are there to teach you grammatical structures.
There are many courses out there which teach you 'useful' phrases from the beginning which you're expected to memorise and repeat in certain situations. Duo starts more slowly, but by the midpoint of a course you're able to construct a variety of sentences and understand their grammar. It takes longer to be able to communicate, but by the time you can you're more advanced than somebody who's working their way through Rosetta Stone or a Teach Yourself book.
Duo gives you the tools to build sentences for any situation, rather than giving you templates which only fit specific ones. It's slower, no doubt, but language learning is a marathon rather than a sprint.
I agree completely on the SRS algorithms. Luckily, there's no reason to keep a tree gold, try downloading one of Memrise's Duo companion courses. You can select words to either ignore or focus on, and the SRS is much better there.
For a company that takes so much pride with their SRS algorithms, they do such a lousy job at it.
This is a core feature, which everything revolves around, and it's more or less broken.
I'll suggest following along with a Duolingo Memrise course for new vocabulary practice.
And Duolingo timed reviews for sentences and grammar practice.