Of course, but for big business it's a fairly big factor.
All raising CT will do is smash small businesses who can't avoid it as easily, thereby tanking the economy at a time when Brexit is expected to put the hurt on things overall.
For what it's worth, I think 20% is fine - don't see any need to increase or decrease it myself.
They are planning to introduce a lower rate of 20% for businesses with annual profits below £300,000.