It all sounds as familiar as the meaning of Life.
It isnt the goal of getting through life itself as death lies at the end, but the journey itself. We create for the sake of creating. If others are entertained or find value in what we create, then so be it. The goal isnt always the end of the project, but small sections of achievement as part of the journey, not just the end.
There are some drawbacks to being the only one that plays our own games. For example, there is absolutely no suprise. We also tend to observe gameplay from a perspective of "what can I change to make it better" instead of just for enjoyment, due to the lack of suprise and mystery that our games can offer ourselves. This is also where we tend to go overboard on quests of perfection. As each of us has both the ability to tweak what exists, and knowledge of foresight, it skews the difficulty. I know how to beat this enemy because I designed it, which robs me of an "aha!" moment where another player would feel a sense of cleverness. Its almost like watching a movie youve already seen before that has a major plot twist. It may be a different form of entertainment the 2nd time through, but the goal has to change to watch a movie a 2nd time. Inception and Fight Club are examples of movies that are viewed differently the 2nd time watching. Playing our own games is similar in that regard. First time through a completed project is a major sense of accomplishment, and usually for the goal of ensuring that a game is playable from beginning to end. 2nd time through our own games causes us to change our goals. 100% collection of all chests. Other achievements. Bug tests. Continuity. Speedruns. It mostly depends on our perspectives.
Personally, I plan on one day releasing a game for the enjoyment of others. But to achieve that, I often change focus to previously completed smaller projects to maintain a sense of "moving forward". I find a lot of times looking at some of my old work inspires new material. Some tricks I may have forgotten, some goals I changed. I look at what I like, and what I dont, then press forward once inspired. If I do play my own games that are finished, I do it so I can remember that sense of accomplishment.