I made a video about this exact subject and I think you should read all the comments on that video, because that gives a good view into the minds of the technical video audience.
It is hard to grow a channel, every day so much new content is added, so much like crypto currency, the chain gets longer every day and your chance of finding the block (or making it through the algorithm to get advertised as recommended) just gets smaller and smaller.
I never paid for advertising, I only mention to subscribe once every 4-5 video or reach out to people to tell their friends about my channel or something like that. I do not have a subscribe template that I shove in peoples faces each video, 3 times with middle-break ads as well, our audience, which is the same people you find on this forum, is just like ourself. So keep making the videos you want to watch yourself