OTH if you use their icons from e.g. Bootstrap as they are usually used then users actually recognize them without thinking and the icons actually help users interact with your website - which is the point of the icons anyway!

The same goes for classic simple buttons, nav bars color pallets etc - users know them already before they interact with your site. Most of that design work you did to make you site "different" or "beautiful" just made your site less intuitive for a user.

This opinion comes from experience building b2b webapps - users generally wish they didn't need to do the admin work the webapp is helping them do. So user stories are dominated by building the simplest quickest workflows to allow users to capture, fetch or manipulate the data they need and to then get back on with their lives - having standard controls that are familiar from other sites helps with this.