Everyone would just take it for granted we'd been invited.

分析：本句涉及两个语言要点：

1. take…for granted 想当然，认为……是当然的。如：

Don’t take all this for granted. 不要认为这一切是理所当然的。

Too often, we take our liberties for granted. 我们常常过于把自由想当然了。

2. take it for granted 中的 it 为形式宾语，其后的 we'd been invited是真正的宾语。

I took it for granted that we’d be invited. 我想当然地以为我们会被邀请。

I took it for granted that you would come to help us. 当时我理所当然地认为你会来帮我们忙。

I just took it for granted that he’d always be around. 我还想当然地以为他总能随叫随到呢。

网友句子的意思：

Everyone would just take it for granted we'd been invited.

大家都只是想当然地以为我们受到了邀请。