"If I don't have high notes, the odds are that I won't ever be a famous singer, right?"
Art isn’t about odds. Art isn’t about statistics. Art is about expressing yourself. It is also about being vulnerable but that sounds scary, doesn’t it. When you sing to express, rather than to impress, that could be a goal.
Think of technique as something that allows you to express yourself, not as the goal. Most singers, when performing, have no attention whatsoever on technique. They have attention on it to some degree when preparing to perform and prior to that, to raising the level of the art of singing which allows the singer to more fully express.
Notes do not have to be high to be good. Singing doesn’t have to be extremely loud to be good. Loudness may affect the outcome of a hog calling contest but with singing, dynamics matter. The variation in loud and soft and in between can be very aesthetic.
Some singers, such as Sade, may or may not have high notes. We do not really know.
I was once told to not go to the extremes of my ability and to stay in a place where I could maintain control and to not have things fall apart on me. I like making mistakes in my practicing, where they are safe to make and only I know about them. In a performance, I won’t wander into a territory of uncertainty. I always go for the art and do it with a thing I call artist’s integrity. My standards are at a highly professional level, one which afforded me the opportunity to sing in a large showroom in Las Vegas. I knew I was good enough.
Perfection exists only as a silly word and an unachievable (and undesirable) level. If perfect singing is staying perfectly in the center of a pitch throughout its duration and if that is sustained, it will not sound human. Some people overuse pitch correctors and they get a “robot” electronic sound. You can hear it on some recordings. Professional standards are actually above perfection, if perfection is staying perfectly on pitch because there is a beauty in being human and not a machine.
High notes are not as important as singing in a smooth connected meaningful way with emotion and more. The more is hard to define but we know it when we hear it. Make it pretty or intense or strong or whatever you want in your song. You can make it interesting to listen to. Music is a hearing art. Listen to many singers and many styles as part of your preparation. A famous trumpet player, the late Clark Terry, gave this advice: emulate, assimilate, innovate. When you achieve this, you will be more than just good and more than just interesting. High notes are not really hard, if someone shows you how to do them correctly and safely.