Yah. I have been renting rentals over the weekend and doing highway driving to get used to the new fancy stuff. Hard to unlearn the past 8-10 years of stick car driving, where you can judge the speed of the car based on which gear you are in, and where you always apply full brakes, rather than light pressure due to power brakes stuff. Never knew driving these fancy automatic new cars with power steering and brakes was so much difficult.On average, rental cars are pretty new, and have the factory tires on them. While these cars are not sports cars, they perform mid pack for the average car on the road. Generically saying every single rental has crappy, dangerous tires is not true.
I would highly suggest the OP takes some additional driver training to give them the skills they need and confidence in their car. In just a day you can go from "but the car just wouldn't stop despite all my efforts." to a much more advanced observation on what actually happened, which means you can actually work on solving it when driving. A remarkable percentage of drivers have no idea how effective the brakes are or how to use ABS and never apply the brakes anywhere near fully.
I think it also comes down to a person getting used to a car. Every time I rent something, it feels different and you have to adjust yourself to the accelerator and braking sensitivity, not to mention the width and hood length.