まるで～ようだ / as if

Hi!
I'm confused about how to use まるで～ようだ. I'm also pretty sure that my understanding of "as if" might be insufficient hence my problems.
I've seen so many grammar notes saying that adding ようだ to まるで changes the meaning of まるで to "as if." I thought that ようだ already conveys the nuance of "as if."

私はまるで夢の中にいたようだった。
I felt as if I were dreaming.

私は夢の中にいたようだった。
I felt like I was dreaming.

I found these two sentences and both English translations mean the same to me. Yet, everytime I ask Japanese people about まるで～ようだ they change their translations to "as if." So what does まるで really do in a sentence?

～ようだ can express the speaker's judgement done by observation other than "as if." For example, 外は雨が降っているようだ。 can also mean "It seems that it's raining outside (judging from the view, sounds etc.)." まるで is used to reinforce the meaning "as if."
e.g.
外はまるで雨が降っているようだ。
It looks as if it were raining outside. (= It's actually not raining.)

However, まるで～ようだ doesn't always mean "as if".
e.g.
まるで日本語がわからないようだ。

This sentence is ambiguous. まるで can mean both "(not) at all" and "as if" here. You need to use other expressions when the meaning is unclear even from the context, for instance どうやら日本語が全くわからないようだ or あたかも日本語がわからないかのようだ.