Manual link building is the SAFER. However, it is time consuming and not cost effective. In the end, if your links are blackhat, it doesn't matter if you build links manually or on autopilot. Mordern link building software like RankerX utilize newer technologies that can simulate exactly what a real user does when it comes to posting to target websites. So in my opinion, using a good link building software is recommended. It is going to save you lots of time and money. And you can spend those resources for content, proxies ... (if you do things manually you still need them).
I personally use GSA SER and RankerX. RankerX is to create my own Web 2.0 networks for tier 1. And GSA SER is for backing my Web 2.0 networks up. Indexing is a daunting task now. 90% of my GSA contextual links are not indexed so I am opting for non-contextual SER links because I only need to pass some link juices from those links to my tier 1 and help index the tier 1 links. And currently, it seems non-contextual SER links are easier to get indexed.
I also have my own PBN, which consists of about 30 expired domains.
How can I manage all of those manually? Using automated tools is unavoidable now.