magento-2-product-slider | Magento 2 Product Slider module allows showing | Ecommerce library

I installed a Magento extension called Mageplaza Productslider using a manual method (copy files to app/code). This didn't look to work, so I installed the extension using composer:

composer require mageplaza/magento-2-product-slider)
php bin/magento setup:upgrade
php bin/magento setup:static-content:deploy

I still couldn't see the extension on any page so I decided to uninstall. To do this I deleted the Mageplaza folder from app/code and ran the following code to uninstall the Mageplaza extension and core:

php bin/magento module:disable <ExtensionProvider_ExtensionName> --clear-static-content

I now have the following error on my Magento 2 product pages on the frontend and when I try to edit products in the admin panel.

1 exception(s):
Exception #0 (ReflectionException): Class 
Mageplaza\Productslider\Model\Slider\Source\FeaturedProducts does not exist

Exception #0 (ReflectionException): Class 
Mageplaza\Productslider\Model\Slider\Source\FeaturedProducts does not exist

To see full error, please see (if links aren't allowed please remove??):

https://www.canvaspro.com.au/horse-canvas.html

I have undertaken the following to attempt to fix the error:

rm -rf var/cache/* var/di/* var/generation/* var/page_cache/* var/view_preprocessed/* pub/static/frontend/* vendor

composer install

php bin/magento setup:di:compile

As I have deleted the var and vendor folders, how come after composer install Magento is still calling for these files under app/code?

Thanks