Are traditional marketing channels – such as advertising, direct marketing, and public relations – still delivering enough value?

Yes, they still do.
Advertising is still very much alive and bringing so much revenues.
Public relations always play a very important role, and I don't think it would ever cease to be effective - unless the universe will be ruled by robots.
Direct marketing is also doing quite well, but the advent of internet marketing seems to have put it second on the line already.

Although Buyers are checking out product and service information in their own way, often through the Internet, and often from sources outside the firm such as word-of-mouth or customer reviews but still Traditional Marketing are important and Its targeting a huge segment of people.

Thank you so much for all

sure in case of the target market can be only reached through those channels you mentioned

While direct marketing is often divided into two camps — traditional offline channels against nontraditional digital channels — smart marketers know that is not an us–versus–them story.
In fact, marketers are finding that the best direct marketing programs are those that marry the best of both worlds with a multichannel integrated approach.