Has Facebook changed algorithms over time significantly to lower the reach of page posts?

I’m a part time pencil drawing artist. 2-3 years ago, one simple sketch on my page would get easily lot of views and around 100 likes. I’m not saying that my sketch was good/bad based on these stats. The point is, it felt pretty normal.

Over the time, I improved my sketching, and started drawing more and more, and reach on my page decreased heavily and likes too.

And now situation is like: I posted a new artwork today and it got no like (it may get 1 or 2 likes later though).

I often see notifications from Facebook to advertise my posts instead. And one more thing. Whenever I don’t post on my page for few months, I start getting page followers automatically.

So does it mean Facebook knows my page has some value and I must be having some money, so I should boost (spend money to get likes) every post. And hence the algorithms are designed to give very low reach to my posts?

If I plot a graph of posts performance over 2 years, it would fall exponentially.

I really don’t think my work quality has decreased exponentially.

Is it just my illusion? Or has some truth about it and algorithms have to do something about it? Does Facebook actually want us to spend money on it?

I will be really thankful to you.

PS: I really want to know this, because if that’s the truth, I’m already wasting my energy on Facebook. I would quit instead.