Since Mac OS X 10.9.x Mavericks, the use of memory cleaning apps seems to be deprecated.

Memory cleaning apps are deprecated on latest macOS

According to "Mac Fan August 2016 issue," the use of memory cleaning apps is deprecated on OS X/macOS since "OS X Mavericks"!

Source: Macのメモリ解放アプリ、「OS X Mavericks」以降は使用非推奨 | gori.me（ゴリミー）

Actually, I was still using memory cleaning apps even after upgrading to macOS Mojave, but after reading this article, I uninstalled the memory cleaning app and stopped using it. I realized this too late.

When I searched for official information sources, it seems there was an announcement at WWDC 2013 keynote (OS X section).

Apple wasn't satisfied with the current state and further optimized virtual memory in Mavericks, actively compressing unused memory to reduce swapping frequency. Even on Macs using SSDs, document opening speed became 1.4 times faster compared to Mountain Lion, and wake from sleep became 1.5 times faster.

Source: WWDC 2013キーノート（OS X編） (1/2)：ドリキンが斬る！（2） - ＠IT

For those who want to know more details, the following 2ch summary article was helpful, so please read it if you have time.

• OS X 10.9 Mavericksに搭載される新技術「Compressed Memory」がなにやら凄いらしい… | AAPL Ch.

How to check Mac memory usage

To check memory usage on Mac, use “Activity Monitor”.

• メモリ | Mac でアクティビティモニタを使う方法 - Apple サポート

That’s all from the Gemba where I want to understand Mac memory usage.