It is very difficult to answer why a Laravel website is slower. There are many reasons behind a slower Laravel application. You have to debug and take decisions where you need to improve in your application. Here a list I focus on when I develop an application.
1. Database
How may database query load on each page? you have to ensure any recursive query not exist. Make efficient data cache. Check queries takes a little time to execute.
2 Network Connection
If you are using different network connections with your Redis, database, queue then make sure those connections are well optimized and taking a little time to connect and serve data.
3. Cache Files
Make Cache you blade HTML files, routers, config files, and optimize those cache. Also, reduct autoloads services as much as possible.
4. Optimize your Images
Optimize your images. I recommend not to use local files. try to use a cloud service.
5. Minify CSS and JS file
You should minify your CSS and js files. and try to use libraries from CDN.
6. Use Queue
Use queue where possible like email send, PDF Generate...