IMO, buying another bike probably isn't going to inspire you to ride more. Having friends that cycle a lot and riding with them might. A change in your health that gets you concerned might encourage you to ride more or some other reason that just gives you that aha moment that gives a shove to your desire to ride more.
Steel, aluminum, carbon, titanium, bamboo and etc are all just materials that bikes can be built from. Higher prices of some are just due to the cost of manufacturing and not that any is particularly better. However the more expensive bikes tend to be made with more care and quality as who is going to pay that much for something that is poorly built.
On a road bike, drop bars are the norm. And for good reason. It gives you several hand positions that you can swap to as you ride which not only helps with giving you a little more aero position to go faster, but also just changes your hands up so they don't stay in one position for 60 miles and get numb. If you are going to buy a bike and swap bars, you need to realize that the bars you pick will alter the way you fit to the bike. And STI's on a drop bar bike won't work well on a flat bar. Getting shift and brake levers might make that simple bar change expensive.
Personally, I'd recommend a drop bar road bike. Get one that appeals to you and the newer the better as it'll have newer components and more gear selection on the rear. Which isn't everything, but it helps to have a choice of gears when riding with others so you can pick the gear and cadence you like for the speed of the group you are with. Which very well may not be the gear and cadence any of them prefer to use as they may be more or less fit than you.
Buy a bike that you can easily afford. That way you can get another after you've gotten some experience, become stronger and fitter at cycling and find that bike no longer does well for you.
Welcome to BF.