How do you really know how good a home is?
The best answer to that is in several parts.
Firstly, visit a prospective home and meet the manager; have them show you around. So you see the place from their viewpoint. While there, see how they interact both with residents and with staff. Do they greet residents as if they were friends? Does the place look clean, does it smell as wholesome as one can expect? If you go there near mealtime, does the food look/smell good? If you don't go there at a mealtime, ask the manager to see a normal weekly menu.
A good home will permit almost unlimited visiting, day and/or night. If this is so, then ask the manager if you can visit another time, without appointment. If you do that, you will see the home from a different point of view. Not worse, just different. Staff behave more normally when their boss isn't there.
Check what accommodation is like. One person per room? En suite? Ability to have own furniture or pictures?
Are residents all stacked in chairs in a room with the TV in the centre? Not necessarily a bad thing, but sometimes the programme will be what staff want - football, soaps, etc. Again, not necessarily bad, but note everything.
the residents don't seem to DO anything
What do you want residents to do?
What stage are they at?
In Jan's home, many are at the stage of being chairbound. Others ceaselessly roam. Activities are, I'm pretty sure, in order to tick some box or other, and to make the carers lives more interesting. The residents generally don't give a hoot.
Some do look at pictures in books.
Don't expect activities to be what you would term activities. But some should be organised, just to give residents a chance.
Should I just be grateful she's looked after
No, not
just be grateful. Be grateful, certainly, but always expect as much to be done for her as possible.
Let any home know that you are actively a carer still and are most interested in her care, and will visit regularly. Make a relationship with the manager, staff, and the other residents, if possible.
Above all, take one step at a time.