Mark my 3 points: 1/ from where you are taking the link, does that site have organic traffic like at least 5k+ ( more is better)
2/Are they giving you do-follow links?
3/Are you taking links from niche relevant site? If the answer is positive for all three 3 points, then yes, guest post still works and it will work till the date the website exists. No update can hit such types of links.
