> The clearest sign a tool is serving you is that you stop noticing it—it becomes invisible.

It is because you are already very familiar with and accustomed to this tool.

The main meaning of the author probably is (from one article):

We need to remember that the purpose of using tools is to solve specific problems and achieve goals.

No tool is perfect. When using the useful functions of a tool, we also need to tolerate or ignore some of its shortcomings. Don't seek out or switch to a new tool simply because of some insignificant flaws. In the process of selecting and using tools, don't have the perfectionism, and always keep the goal in mind. The important thing is to master the useful functions of the tools to quickly, effectively, and efficiently complete tasks or goals, thereby significantly improving efficiency and productivity, rather than constantly complaining, switching tools, and wasting time and energy.

For the tools we choose, one must become truly familiar with and proficient in their use, continuously customize, modify, and improve them, and strive to use them to the fullest extent, thereby significantly improving efficiency and productivity, and solving practical problems and achieving goals faster and better.