I want to know where all these "indoor homes only" rescues are!
When I first got mine, cats that needed to be indoor only was at the top of my list; I don't live on a busy road as such but I know plenty of people who have lost cats to cars, we have urban foxes here, at the time we had a very aggressive local un-neutered tom who beat up all other cats, we have people doing car mechanics (anti-freeze is deadly to cats), and of course a reasonable population of thuggish little scrotes roaming around who I wouldn't trust near any animal let alone a cat.
My garden isn't cat-proof-able except at great cost (mid-terrace, assorted conservatories, various other factors), and a catio would be even more expensive due to living in the side of a hill with a terraced back garden. So indoor it was.
I spent AGES trying to find a pair of cats who didn't need access to the outdoors according to the rescue. I was happy to take special needs, elderly, FIV/FIP positive etc. Ended up going about 50 miles to a rescue that was open to letting me adopt indoor cats - in fact mine had "must be indoor" in their adoption contract - while I must have around a dozen or more good rescues in a 15 mile radius.
My pair have been content since they moved in. A little curiosity about outside yes, but no trying to get out, dashing for the doors etc. They have the run of most of a 3 bedroom house, plenty of places to get up high, stay low, hide in, stretch out etc. Loads of scratchers which they use, assorted types of toys, play time every evening (if they want), a mahoosive cat tree. Each other to chase, play fight & wrestle with, snuggle up to etc.
Over time it has become clear that Boycat is ND with "issues" - thick, no attention span, clumsy, nervous, scared of everybody except me, my DSis & Nephew no. 4, and especially terrified if any other man comes in the house. He's got a scar on his face, and we think he had an accident or was hurt when younger and he would NOT be safe for 5 mins in his own back garden. Vet refers to him a special needs and says it's a good thing he's indoor only.
Over 6.5 years apart from their MoT up until this autumn they had a total of 2 visits to the vet between them. Girlcat was doing loads of foamy vomiting so took her in just in case - worked out later that it was probably the enormous spider she'd eaten. Boycat had cherry eye, knowing him he'd walked into something! Unfortunately since then Boycat has been diagnosed with CKD, but the vet has assured me that it's despite his lifestyle rather than because of it and probably genetic. At their MoTs every year they have been pronounced as exceptionally well and healthy.