Fancy Feast Medleys Primavera is the only canned food my cats will eat. While it's not the healthiest food out there, I will say that even the cheapest canned cat food is better for your cat than any dry food. If you can get your cats off dry food and onto a canned only diet, that is 90% of the battle right there.
Dry food simply does not give your cat the nutrients or moisture they need. As ancestors of desert dwellers, cats have a very low thirst drive. Canned food is about 75-80% water which is about the same as a mouse or bird. Dry food is only about 12% water. By the time your cat goes to the water bowl, they are already severely dehydrated. They will never make up the difference at the water bowl and will remain in a chronic state of dehydration which can cause long term issues like kidney disease and crystals that can block the urinary tract.
Also, Fancy Feast has many different versions and I would not make a blanket rule as to healthy or not healthy. Their pâtés are probably the healthiest as they are the lowest carb. Gravy versions on the other hand need to have thickeners which increase the carb content. And don't fall for the "grain free" claim as many grain free options substitue other fillers such as pea or potato flour which are no better than grains.
So don't focus too much on brand but rather ingredients list. The best canned foods have the first five ingredients from an animal source. The trouble is meat is expensive and cuts into the pet food companies' profits, so they add other junk. Cats are unable to metabolize plant proteins as they are obligate carnivores. This is why the protein content under guaranteed analysis is misleading because this can be quality animal ptotein or it can be plant protein which is useless for cats. Note that healthier cat foods actually have a higher fat content.
And here is the tricky thing about labelling. For example, if your cat food says "Chicken Dinner" that means it must contain at least 25% chicken. However, if all it says it "Cat Food with Chicken", that means it only must contain 3% chicken. Note that you with almost always see the "with" word used on dry foods. Even if the first ingredient is chicken, it may still have very little chicken in it.
Also note that Fancy Feast is made by......Nestlé Purina, so going to something like Purina Pro Plan or Purina One will most likely be a lateral move and not necessarily a healthy one.