We currently have 11 cats and we have lost others previously.
My family cat Polly was run over (10 years ago) Totally drivers fault
Second family cat Mitzi, who went outside, died from cancer.
DHs family cat Salem, was an inside cat, was PTS at 8 years old.
DHs second family cat Tommy, lived 13 years inside, then went outside for about 5-6 years, was PTS at 18 ish.
Our Abby Mimi was an inside cat due to age, died at 5 months old from a tragic mirror related accident.
Our BSH, Lady was an outside cat, was killed by foxes at the age of 2.
Our Nala, was an inside cat (her choice), died at age 2 from a lung problem.
Our George, half Bengal, my pride and joy, was an outside cat, died suddenly, outside from a heart attack type incident at age 6.
His son Suru, was an outside cat, and our neighbours tell us he was run over by a tractor, although there was no evidence to support that age 7.
My point is, I guess, is that out of all of these only 2 (maybe 3) are as a result of being outside cats. I do believe that cats live the fullest of lives by being allowed outside.
Of our current 11, we have only 2 adult cats who are not allowed outside, one (Bumble) suffered mild brain damage at birth, and the other is a rescued Savannah cat (Zelda) who was abused, but also so incredibly friendly she would wander off following someone or be very easy to steal, but more importantly hasn't shown any interest in going out.
We have 4 who go out all the time (Lennon, Shinobi, Teddy and Tux), a 5 month old Maine Coon kitten, Nova, whose not ready, the 2 who are not allowed out, then we have 1 boy, Remi, we are trying to get to go out, and then 3 girls who are allowed out Momo, Pixie and Cici. Momo will go outside maybe once or twice a year, and the other 2 will sit at an open door or window and have no interest in going out and never have done.
I would try and let your kitten outside, maybe look at a catio if you are worried. With our Maine Coon, I am very aware how he stands out, his pure white and theft has crossed my mind, I am hoping he will be the type to frolic in our garden and not explore too far.