There is honestly only one way to make your site TRULY mobile friendly. Seriously. People have talked about it for years. Google makes a little “mobile friendly checker” that they have tucked into Search Console to help you with the process. It will either give you a “thumbs up” or a “thumbs down”. But it is time for some up front honesty.
The ONLY way to correctly check the mobile friendliness of a site is to spend some quality time with an iphone in your hand and go through your site. Pro Tip: Go to Google Analytics and find your mobile traffic. As a secondary dimension find the landing pages that people LAND on your site for currently. Then go to EACH and EVERY one of them.
Within a page or two you will LIKELY find something that REALLY frustrates you. Fix it. Then move to the next thing that makes you want to throw the phone against the wall. Lather.Rinse.Repeat.
Then grab a droid and do the SAME EXACT THING.
But that is time consuming, you say. Indeed. But that is frustrating you say. Indeed.
I would say this. If you had a bricks and mortar store and something in that store was frustrating your customers and driving them away…would you fix it or leave it there?? Same difference.
Just my .02