포함하다 - to include.
포함되다 - to be included.
-되다 verbs are often passive forms of the corresponding -하다 verb.
Can someone explain why 우리는 포함됐다 is wrong?
I guess that would kind of mean, 'we can include' or 'we did include'. Whereas 우리가 포함됐어요. means specifically past tense - 'were included'
I don't understand why. 포함되다 is the infinitival form. 포함됐다 is simply the written (past formal low) form of the past tense (like 포함됐어요 is the formal form [present formal high]). See this page.