ModSecurity, as with any Firewall (it is a web app firewall after all) is only as good as its rule set.
Owasp is a very in depth rule set, and as noted well in this thread, requires some customization. This is a caveat of OWASP more than ModSecurity itself. Some rule sets like Comodo require much less pruning.
At this point in the industry, there are several amazing providers out there that offer managed/cloud WAF with a much more hands off experience. Of course I guess like anything there are trade offs to open source vs commercial solutions. However if you are a shared hosting provider, it's very worth looking at companies like cloudflare, sucuri, or sitelock. They see every hack going on across many customers, and it's much more efficient to offload that work to people who have done the research for you and can clean it reliably.
I personally recommend a combination of both, modsec by default, and 3rd party layers as an added service option.