Facebook groups, Marketplace and a business page can absolutely help a contractor find work. The issue is not whether Facebook works. The issue is what happens after someone sees the name and decides to check the business.
Social media can introduce the business. A website gives the customer somewhere stable to verify it.
Customers check more than one place
A homeowner may see a recommendation in a group, search the company name, look for reviews, examine project photos, and only then decide whether to call. A website connects those pieces and lets the business control the explanation.
Social platforms are rented space
A page can be useful, but its layout, reach and account access are controlled by someone else. Important information gets buried in a feed. A website gives services, contact information and proof of work a permanent structure.
The website does not need to be large
For many solo contractors, a focused site is enough: a strong homepage, clear services, areas served, trustworthy proof, and a simple way to call or request an estimate.
Use each channel for its strengths
Facebook generates conversations and demonstrates recent activity. The website converts curiosity into confidence. The strongest arrangement is usually not one or the other, but a straightforward website supporting the channels already producing attention.