More and more website owners are pointing to their Google page speed score. See: https://developers.google.com/speed/pagespeed/.
The speed of your website is an extremely important factor, users will simply not use a slow website. Many do not realise Google page speed is not actually a complete indicator of speed.
See Google Page Speed cannot look at some of the most important factors to make your website fast such as server caching or the way the database has been indexed for speed.
Our advice is to not blindly trust the Google page speed tool, worry about the speed of the website as you use it and not chasing a higher grade. It can give useful insights and tips, but let your web developer look through the results and recommendations and decide what is doable and what will really help you. It is a very useful tool as long as you understand it.
Note there are other tools that can be used such as Pingdom, see: https://tools.pingdom.com/ that provide a better indication of the speed a page loads.
Also, please note speed is not only important for usability, Google has advised it is also part of their SEO algorithm. A fast website is a good website.