Niche matters almost more than anything
Many people feel sad about their growth. They see others with massive growth and tons of subscribers. Then when they examine those people's work they find it to be the same quality as their own.
Niche matters.
If you are growing slowly, you may be in a "boring" niche. You will never grow as fast as someone writing in health, money, growth-hacking or relationships. Sure there are definitely things you can do to improve, but you will likely never be a rocket.
And that's ok.
You might make more money from a smaller, wealthier audience. You may enjoy a small audience more.
Everyone's journey is different.
(And this is from me, writing in the boring niche of project management. It's taken me 3 years to get to my current 2500 subscribers.)