Yes, hosts do not support wildcards. There are some solutions to blocking advertisers that use tricks like you suggest. A PiHole is able to do wildcard blocking

Yes, hosts do not support wildcards. There are some solutions to blocking advertisers that use tricks like you suggest. A PiHole is able to do wildcard blocking. Also, uBlock Origin (which accepts host formatted lists) will automatically block any subdomain of a blocked root. So as long as the parent domain is also blocked, any subdomains would also be included