Is SEO is enough for making a business successful?

No way...a lot of visitors or good SEO does not mean you are getting even one sale.

Prem According to me, SEO is only a part of any business promoting strategy. It helps to promote your business. It makes your business accessible for people, however it cannot provide you sales or money. When a visitor comes to you by SEO, you have satisfied him about your business and products and this can be done through your sales persons. There is a big team and effort behind a successful business. Still consider advertising within the press, radio, using business cards, brochures, networking and more. Don't think about only one part of any business promoting campaign.

If SEO can be utilized in proper way, then SEO is enough and otherwise that is not enough.

SEO, so far is the most important tool to make a business successful (online). However, there are other factors present which helps each other building the pillars of success for that business. So, you have to focus on every single factors.

Having good SEO is not to make your business successful, it is only to promote your site online which help your site get high ranking in search engines and attract people or increase traffic to your site. But it does not confirm the increase in sale.

SEO is not enough you need many more things also

No. SEO can boost traffic to your website and improves the search engine result. This does not warranty to boost your business sales!

No. All SEO does is bring people to a site. It's the conversion of that traffic that leads to success.

Compare it to a physical store. A physical store that attracts 1,000 people, but only sell to 10 of them will make less than a store who only attracts 50 people, but sells to 20 of them.

Hardly. If your business model is crap and your value proposition nonexistent, letting more people know about that isn't going to help you.

No. It won't make up for having a crappy product/service.

Absolutely NOT.
Libraries can help you learn about the process of becoming self-employed locally while building a business