Umezawas Jitte Umezawa's Jitte was banned preemptively in Modern when the format was created because of its insanely valuable ability to just completely hose aggro decks
Amusingly, the way the top 8 players were paired up meant the final day of the Pro Tour featured mirror match after mirror match, with six bouts where a deck faced off against a nigh-identical clone
Your legendary stuff gets a boost in size equal to their count
Sure, there are times when your combo-esque cards don't really come up in the right sequence, but that's pretty rare
For example, if the exiled card is a land card, you may play it only during your main phase while the stack is empty and only if you have an available land play remaining
If the answer is none, then don't worry about adding them in at all