Is it possible to downgrade a website without cms?

Question

CMS

Tell me, is it possible to lower the Yandex search results if the site is without cms?
In general, the site is written in pure html, etc. There has never been a CMS on the site, the company has been promoting the site for half a year, now they say the site has fallen in the search results and their experts say that this is due to the fact that there is no CMS recommended by WP.
But if you pull the site on WP, you will be happy.

Answer 1

Downgrading due to lack of cms? Seriously? Spit in the face of the one who said it.

Answer 2

PS doesn't matter, they see html and that's it.
And they recommend you VP because they know how to put SEO plugins on it with the mouse, but they haven’t learned how to do it manually.
Or they want to increase the budget due to installation, settings, etc.
But if the site is growing on 100,500 pages, then in general it is more convenient to manage all this on the CMS.

Answer 3

Amateurs, if not worse, not specialists. The presence of a CMS and the fall of the site's position are as connected as the elections in Nigeria and the Bitcoin price.
Most likely, something went wrong with the "specialists", so they are looking for excuses. Although if you actively start moving a site that was standing before, then six months is not a time for a general assessment of activity.
In any case, let a third-party SEO specialist look at the site, he will tell you for sure if there are jambs with promotion.

Answer 4

Of course not, besides, the search engine does not suspect whether you have a CMS or not