You need to find a different word that isn't "lazy".

Perhaps a better way to say this is: restaurants are good at being restaurants, but aren't always good at establishing an online presence. A big part of why these delivery services succeed is that they provide a function that restaurants aren't well suited to provide on their own.

This isn't about being lazy, it's about an industry needing to adapt to the new expectations of the app economy, and often not having the expertise to do so.