We have rebuilt enough sites to notice a pattern. It is almost never the colors. It is that the site loads slowly on a phone, does not say plainly what the business does, buries the phone number, and was built with no thought given to how search engines read it. Every one of those is fixable, and none of them require the biggest package anybody could sell you.
The site you are reading this on is the standard we hold ourselves to: it is static, it loads immediately, every page has its own structured data, and the phone number is one tap away from anywhere. We are not going to build you something we would not put our own name on.
A website is also where everything else lands. Every post, every ad, every Google listing eventually sends someone here. If the site does not convert, the marketing budget in front of it is being spent to fill a leaky bucket — which is why we usually recommend fixing the site before scaling the spend.