In short, YES! Except from affecting the user experience during browsing a website or anticipating for it to load, it severely affects how search engines index your website.
Search engines prefer fast websites without too much unnecessary coding and big files. So, an optimized website can severely affect it’s visibility and popularity on search engines.
Gladly, there are many solutions to increase speed. It’s not a one-fit-all solution to the problem but you can start by the basics.
There are tons of plug-ins for various CMS’s that you can easily install and configure. While there are some plug-ins that simply “trick” website metrics into displaying better performance insights, there are many decent ones that can actually improve website performance.
Our preferred plug-in (for WordPress) is Speed Optimizer (previously SG Optimizer) which is developed by Siteground. Up to recently, it was only available for Siteground clients, but they enabled for all hosts! You can see a live example below.

A popular metrics tool is GTmetrix, but there are plenty of alternatives.
While achieving A rating is not an easy task, getting as much high as possible will positively affect your UX. This tool allows you to pinpoint which elements of your website affect speed.
The caching tool will allow you to fix those issues and improve website speed. You can enable various caching features, compress image files, pre-load fonts and even pre-load external links.
In Dystopia we strive to get as much performance as possible with our client’s websites because that in the short and in the long run it will improve user experience and SEO.