WordPress core is not heavy, but the themes, plugin you use may slow down the overall page load time. There are many techniques to speed up your WordPress website. I know was a lot of people installed too many plugins and a very heavy theme, and the site started to load very slow. I have an online shop, and I have installed a lot of plugins and animations with a theme with animations, and after I installed the WordPress price calculator it started to glitch. I didn't know what to do so my friend recommended hosting on performance-optimized server.
