Is it possible that you can successfully complete the optional task from tradecraft where you have to enter the base through the front entrance? I tried doing this but I failed the task for some reason. The elevator was blocked by a book shelf or something like that. I ended up going through the escape tunnel after. Is it a big deal that I did not complete the optional task successfully?

It's always blocked as far as I know.

You will always fail. You can open the bookcase like it's a door, but the elevator is powered down, so you have to take the other route afterwards regardless.

I found the Switchboard pretty early on tbh, but I didn't do Tradecraft until just last week. And I started playing at launch.