Bikes are designed weight and geometry wise to handle a certain way with certain bars, weight distributions and angles. If you change the bar you are going to significantly change all those factors and the bike won't handle well.
Case in point I recently did an Emonda SLR build. My other bikes are pretty upright, I got an angled stem for another drop bar gravel bike because I hated it. Of course in the last few years I hired a personal trainer and engaged in a very serious fitness journey. For the first time since I was on a college varsity team exactly 25 years ago, I was able to touch the ground with my fingers while keeping my knees straight.
So anyway I was afraid of a very "low" position so I started the build with a higher angled stem. It wasn't bad so I dropped it and eventually went to the handlebar Trek recommends for that bike, almost a Tour de France type position. Didn't bother me; it would have years ago but this was just fine. However, the lower and more bent forward I was, the better the bike turned and handled because of course, the Emonda was designed to have the rider in a very aero, far forward position with plenty of weight over the front tire. Not doing so even by a little resulted in worsened, much less sharp handling.
So I went back and put the original stem on my Warbird replacing the angled one. Indeed, then too the bike's handling improved significantly with much sharper turn into the curves. It's also more stable on trails while descending and doesn't jostle around as much. Just 20 freaking degrees.
So for you, you should do one of two things:
1. Engage in better fitness and flexibility so you can enjoy the drop bar again. Not easy but worth it. You can do it at any age, you'd be surprised at the long term results if you are very consistent in a stretching, body weight and light resistance regimen.
*OR*
2. Sell your current bike and buy a new one with a flat bar offering whatever body position you like.
You can get an angled stem to make the bike liveable while you engage in #1 but be prepared to have it negatively affect the bike's handling to a degree as it did for me above.