don't think of smart contracts as something weird or advanced. they are pretty simple actually. and they can be done on bitcoin but bitcoin is designed to be a currency so the functionality will be limited.

but the good news is with side chains such as RootStock (a project that was being developed for a long time) smart contracts will not only become possible but also will become an easy, cheap/free, and fast thing to achieve. because it is no longer on chain and it will be super fast and ultra cheap unlike what ETH is offering.