Does the publishing platform matter for SEO?

As the Wix SEO Haters (https://www.wixseohaters.com/), we'd say so ??

But no in all seriousness, I'd agree with your answer "sort of but not really". Yes, as others mentioned, platforms like Wix are going to restrict flexibility and  add excessive overhead and fluff that will slow down your site (which seems to be trending towards holding more weight in regards to SEO).

However, with the right strategy and research in place, you can have a pretty effective SEO campaign, regardless of platform. Just some make you work a little harder than others.

Wix has definitely made a vast amount of improvements which has enabled them to evolve from a definite no in the SEO world, to an option for small businesses with little to no budget.

I guess it all depends on goals, resources, and industry/business type.

I'm completely with you regarding pure HTML / CSS being my preference. Reason being you have 100% flexibility. Just about every CMS spits out unwanted "fluff" which is just unnecessary. I know when a website is using Wordpress within seconds of looking at the source because it's an absolute mess. 

I think all these studies are pretty bias. From my point of view, the smallest businesses who barely know how to switch a computer on will choose Wix, and somebody who knows their stuff will pick Wordpress, and large business with developers will probably go for a custom build.

Therefore, CMS aside, who do you think would rank better? Clearly, it'll be the business who puts more effort into their website! 

In my opinion, the CMS only really matters if it restricts you. I've never used Wix myself, but using Shopify as an example -- I know you pretty much live by their rules, so for this reason (lack of flexibility) I'd go elsewhere, perhaps a custom build or Magento.

I'm completely with you regarding pure HTML / CSS being my preference. Reason being you have 100% flexibility. Just about every CMS spits out unwanted "fluff" which is just unnecessary. I know when a website is using Wordpress within seconds of looking at the source because it's an absolute mess. 

I think all these studies are pretty bias. From my point of view, the smallest businesses who barely know how to switch a computer on will choose Wix, and somebody who knows their stuff will pick Wordpress, and large business with developers will probably go for a custom build.

Therefore, CMS aside, who do you think would rank better? Clearly, it'll be the business who puts more effort into their website! 

In my opinion, the CMS only really matters if it restricts you. I've never used Wix myself, but using Shopify as an example -- I know you pretty much live by their rules, so for this reason (lack of flexibility) I'd go elsewhere, perhaps a custom build or Magento.

It goes without question that WIX produce some fantastic looking websites. However within the SEO world they are still a bit of a joke. So much so they put up a competition to build a website using any backend platform to beat their offering for a keyword phrase of SEO hero. https://www.wix.com/wix-lp/seo-heroes The contest is closed now before anyone rushes out to build a site.

This contest was really quite flawed as the hype around the contest and the chance of winning $50,000 meant it created a lot backlinks for WIX which in turn would boost their profile. Well why else would they give away $50k 😀 Quite clever marketing and SEO strategy really when you think about it even if it pointed out one of its flaws.

But as has been pointed out, all CMS's generate HTML and no matter how pretty a website looks that does not translate into how well a site will rank. 

A good CMS though can generate good onsite SEO, which can leave the webmaster the spare time to work on off site SEO. Although I am not a huge fan of wordpress, it does do a pretty good job with a few extra plugins of handling a lot of boring things. However it also produces a lot of bloat so for clean prefect code it comes down to hand crafting a custom site. 

I come from a period of time when page size was paramount, I would remove everything from a page that was not required before publishing. If you looked at the source it would be 1 line of text with all comments, carriage returns, double spaces etc removed. Even ID's and class name where reduced to single or double characters as every single byte counted to the overall page size. On a really busy site these few bytes saved would enable us to serve a lot more users over the same bandwidth. 

There is a possibility of platforms affecting SEO ranking as platforms such as Wix have come up with necessary upgradations making it one of the convenient platforms to work upon.

Yes they are important and it will give benefits to SEO.