The truth is you need both style and substance. Your deck needs to be better than 99/100 others. Though design is just the icing on the cake to take you from 95/100 to 99/100.
Yes but my point was clear: substance is hard to get right, and it's better time invested working on it than trying to optimize your deck visuals.
My approach is to spend 98% on substance, then use a template (like Beautiful.ai) or contractor to quickly put together something visually appealing. Doesn't have to be a unique design, but for under $100 or a couple hours time, I can get something that's just pleasant to look at.
thats one of the best ways to go about it. delegate that design task to someone or something that is good enough so that you dpnt have to worry about it.