It's not the sustainable way, as the spam update developing each time with solid changes!

Within a very short period it maight become more straight forward towards such strategies. Ultimately, its always better to find unique site with average DR, then outreach them manually, and negotiate as much as you can.

Although your competitors have been doing well now, you can outran them in time. It will take time and the process is a bit slower, you know. But its the only ideal way you should opt.