The clause retaining ownership is there for the animal's protection, to prevent a repeat of the kind of situation that caused the poor critter to end up homeless in the first place.
In practice for a good owner this clause is not onerous at all; once I had convinced the shelter that I would be the right owner for each of my mutts, what further contact we had was initiated on my part as I became a supporter of the shelter. I've never felt constrained in any way because I am the 'Halter' not the owner. I have made all decisions, major and minor, on my own. When the sad day comes and I know my friend is facing a terminal diagnosis I inform the shelter, and every time the response has been the same - sympathy and trust that I will do the right thing when the time comes.
The retained ownership clause protects the animal from an irresponsible owner. If an irresponsible owner is found to be in egregious violation of one of the conditions of the adoption contract, if the animal is found to be living in abusive conditions, the shelter has the right to take the animal back. If an owner for some reason can no longer care for his pet the shelter will take the animal back, or one could recommend a new owner and the shelter will go through the assessment process with that person, then if they agree do the transfer. Either way, the animal doesn't land on the streets or in inappropriate hands.
Be aware that most shelters will require that a cat be neutered or spayed, baring any medical contraindications of course. This is central to the mission of most rescues, as overpopulation is a main driver of homelessness - and misery, and untimely death. Most will neuter before adoption, but in the case of an animal too young to be neutered many will ask for proof, that is, a letter from the vet, that this has been done at the appropriate age.
It's important that you read, understand, and honestly agree to the contract. Most of the shelter's policies will be on their website, read those before you inquire about an animal. If there is a clause in the contract that you feel you cannot live with, then the answer is simple: adopt elsewhere.
I should point out that AFAIK legal liability remains with the Halter even in a case of retained ownership by the shelter.
But really, the retained ownership clause is something you should be glad to have, it's peace of mind for you, too, knowing that there is always a 'plan B' available to help your pet should the unforeseen happen. It's not something to worry about, seriously.
Anyway, good luck with your search, I wish you and your future furry friend all the best.