Over the years there have been many opinions on what CMS offers the best search engine results for your web site. Many of these opinions deserve some consideration, but the bottom line is...
Search engines don't care what you use for your web site !
That's right, unless you are using a system that obscures your site content, you're good. Yay ! Now here is the bad news.... Content is King. Talk to anybody who is working on organic search engine rankings and they will confirm the mantra, Content is King.
You need a web site that has a lot of information (content) and somebody has to write it and prepare it. This has proven to be a big stumbling block for some business owners. Search engines read text to compile the rankings they calculate. CONTENT, and lots of it ....and your rankings will improve regardless of the web site generation.
Thinking that I will rank high for anybody searching for "web designer" is unrealistic and very expensive so considering my SEO budget I will go for some alternative, reasonalble search results. I specialize in Joomla so I want to be found by somebody searching for somebody who works with Joomla. My nearest keyword friendly town is Vancouver, WA and it would be nice to do work with local companies.
With that in mind, I am targeting people who are searching for a web designer in Vancouver, WA and/or need somebody who works with Joomla and all my content reflects that.
I will use my own site as an example of some "good practices" to consider in content creation. Ideally every part of my site will reflect the keywords I have chosen. Menu names /aliases will be specifically chosen with my target keywords in mind. Image names, links, titles, and meta information will all include specific words. A photo I use might be named "Joomla-New-XYZcompany.jpg" instead of "IMG4589254.jpg" and my portfolio page title is "Portfolio web design Vancouver,WA" instead of "Portfolio".
Once you have the content of your web site managable, (note: it is never "done") the next consideration would be incoming links. That is, other credible web sites that link to yours. Lets consider "Cher" - Search for Cher and the official site for the performer Cher is #1. Is cher.com filled with content and optimized in every way to rank #1 ? No. There are so many other web sites that link to the official Cher site that is all they need to rank at the top.
Mobile Display - if Google doesn't think you have a mobile display. Your site won't rank on mobile devices. Don't miss on this huge market, check your site here : https://search.google.com/search-console/mobile-friendly and if it fails get it fixed.
This is a simplictic overview of what could be a very complex process. There are many other things to consider, page load time, sitemap creation, social networking, open graph urls, structured data, .. and the list goes on. These extra considerations become more important in a competetive marketplace, but the good news is that my experince has shown that good content alone can organically rank high in no time for niche markets without a lot of additional marketing $.