They should at the very least give some rationale to all their decisions/advices. With a design decision it might be hard to produce metrics and data on the spot, but they should be able to quickly draw on the whiteboard the overall architecture, with some pros and cons.
And this probably something you should do with less senior people.
So maybe investigate a bit about X and Y, and if you have some questions, or some blocking point, you go back to your tech lead and ask him.
'You know I have been looking at X, and I think we will have some issue to test it. (or deploy it/ maintain it/etc) How do you think we will handle that ? From what I understand using Y will solve that ? What do you think ?'
Knowing what to do is important, but often knowing what to NOT do (and why) is more crucial. If you are working with more senior people, try to learn as much as possible from them. By asking 'deeper' question, you'll learn something anyway.
But between the line, I understand that maybe your tech lead/architect do not really believe in teaching/increasing the knowledge of its team member. And obviously it is harder context to learn or challenge decision.