I'm a dog walker and cat sitter (ie visits in cat's own homes).
Until doing this job I did feel that the majority of cats are happier with free access to the outdoors- based on the many cats that I have owned.
I've changed my opinion having cared for hundreds of cats in their own homes.
I now feel it really depends on the cat. Some indoor cats really are not bothered about being outside, others you can tell resent the confinement and want to go out.
Some cats which are allowed outside choose not to leave their garden. Others roam far and wide.
I believe if you have a cat that is one of those who has little or no inclination to go out then it's absolutely fine to have an indoor cat.
The problem can be finding a cat that feels that way. You certainly can't tell when it's a kitten....
Lots of people think pedigree cats don't want to go outside. IMO this is an unfair generalisation- born from the fact that they are worth huge sums and owners more often choose to protect them by not letting them go outdoors.
Only one breed, the Ragdoll seems more prone to not be bothered about going outside. Apparently they have had many cat instincts bred out of them which makes them less adventurous and less streetwise.
If you have an indoor cat you have to be extremely vigilant about doors and windows unless you have a cat which shows zero interest in the outdoors. They can become very adept at dashing out of doors on dark evenings and it's really hard to prevent this.
I'm sorry you've lost so many cats to the road OP and I completely get how you feel
.