I have met many clever people who are members of churches, but their time given to their churches is voluntary.
Often the equipment has been donated as well, and so is usually not particularly modern either.
The website design is usually managed by a committee, as is the choice of hosting provider, and costs are kept to a minimum.
The net result is that once the web site is finally done, it may be neglected, or someone inherits the responsibility for it who knows little about its history, and might be more secretarial than technical. Thus security updates get neglected, and quite often there are many user accounts with weak passwords.