If you are going to run your site with wordpress, you need a good hosting provider. But more often than not, people pick a low cost provider and their site runs slow.
Note: Although you can 'view source' on any page and often find out what theme they are using (if it's a wordpress site), you might find it easier to use What WordPress Theme Is That?.
For years, I have been frustrated with Wordpress. It's overkill for most websites, requires more costly hosting, and can open you up to problems when others (including the website owners themselves) gain access to the backend.
Regardless of my preference not to use it anymore, I still have clients who do. So my goal with this page is to bookmark 'go to' support articles when you need them: