It can be very time consuming, but IMO visiting care homes yourself is really the only way. Having looked at masses for both FiL and my mother, I'd always discount any that ask you to make an appt. for just an initial look around. And trust your instincts - if it doesn't feel right then it probably isn't.
Might add that the worst I ever visited by a long shot, was very expensive and the most 'luxurious' - on paper, and possibly at casual first sight.
An elderly aunt of dh's (no dementia) put herself there for a month, while her cleaning lady/helper was away.
Despite outward appearances - plush and sea views etc. - it was horrible. The staff were surly and miserable, the atmosphere was not at all welcoming. When I once happened to visit the aunt at lunchtime, I was very curtly told I couldn't stay in the dining room, I was in the way. (I was in nobody's way.).
The aunt couldn't wait to leave.
The atmosphere was so radically different from the CHs we eventually chose for FiL and my mother - so warm, cosy and welcoming.
However it was a very useful lesson in not judging by appearances, 'luxury', or bells and whistles.