This question recently was closed as "too broad": https://drupal.stackexchange.com/questions/138290/homepage-is-loading-very-slow-while-internal-pages-are-faster.
As it was originally written, it was clearly too broad, so closing as "Too broad" was IMHO a correct call.
However, after it was closed, the OP added the following information to the body:
EDIT: I found what causes this slowness: it was a views block (visualization of ~5500 nodes). That block was visible only at homepage. After setting the views cache on views settings page, it's OK now.
Now, IMHO, that was a sensible edit. It added relevant information that narrowed down the question. The question can now be answered (Answer: You need to fix the views cache settings.) This could even have been added as a self-answer if the question had been re-opened). I consider the edit made by the OP helpful (e.g. if somebody were googling for "slow drupal" and found the edited version of the question, they would learn that a bad views cache could be a possible cause of the slowness).
However, the diamond mod decision here was not to reopen, but instead to roll back the question in order to make sure the question stayed too broad to be un-answerable.
I just wonder: What is the rationale behind deliverately removing information that is added to the question by the OP in order to make a "too broad" question answerable? Are such removals of information aligned with the best-practices of the community?