By adding it this year, my return has gone down significantly. Don't see how it benefits me.
You can't choose when to use your tuition. You have to claim your current year’s federal tuition fees and any unused tuition amounts carried forward from previous years on your current year's tax return. If there is an amount left over, it will be carried forward automatically.
As for why your return goes down when you enter your tuition, if it's it's tuition for this year, then it's Canada Workers Benefit (CWB) dropping off. Students are usually not eligible for this credit, so when you tell TurboTax that you have tuition, then the CWB is removed if you no longer qualify for it.
Other credits can drop off as well, because the tuition credit has to be used first. So, if you are claiming tuition carried forward from last year, then that's what's likely happening.