Capital letters give away some answers
I've noticed that whenever you get a question where you have to build the sentence from a list of words... the capital letters always give the first word away. It would be better if no capital letters were given for the first word of the sentence. That said, it could be useful to include some capital letters (and their incorrect counter parts) for things that aren't capitalized in Spanish but are in English (or vice versa) . For example: language names... español y inglés.
You say that and whilst I do agree it gives the user more of a challenge, it's so annoying when you word something a certain way and they say "this answer is wrong" and you have to report it, and type in another answer, and if you've ever been in my situation then it gets very VERY irritating when you're stuck on a lesson because Duolingo wants you to word it a certain way, and ultimately from that I finish the lesson and through my frustration of having to type a sentence a certain way, I find out that I've learnt exactly 0 words from that lesson.
Yes, I do see and appreciate your point, it can be annoying. However, I prefer that, as I want to know why what I've typed is wrong. Only by duolingo marking my answer wrong, do I get a chance to understand why it's wrong and what I need to change to make it correct. You don't get that by using the words duolingo gives you.
That's all part of the learning process for me, which is why I have those words permanently switched off.
Actually I always try to complete the exercise verbally first without trying to look at anything else... drop downs or word lists. Then I review those things. So while I agree with you that it is much better to complete the exercise on your own I disagree about doing away with them all together. Sometimes they give me a way to translate the exercise that I didn't think of which expands my understanding.