How Effective is HARO link building technique in Digital Marketing?

I am managing a digital marketing and firm by name of RS SEO Solution (https://www.rsseosolution.com) .... We search always for new and effective link building technique to get high quality backlinks for client's projects. We listen about HARO link building technique ..... A bit hard to work on this because need high quality and informative contents, So needy journalist or person can use your contents to his article or essay or news with your website links. But really this process is good way to get high quality backlinks to build authority and ranking. What do you think about this technique??