I worked in care a long time and this, unfortunately, is not uncommon.
It's what happens when care is a profit making business first and foremost and the staff bill is one that can be cut with little in the way of concequences for the people making those decisions - when things go wrong it's the care staff that take the fall, sometimes the management but very rarely the people refusing to provide the resources needed to provide a decent level of care.
This sounds harsh and sarcastic and I don't mean it that way, but, we can expect and even demand standards improve as much as we want, when the resources aren't there to deliver those standards it's impossible.
There's no legal minimum for staffing levels, it must just be 'safe', ie the residents needs are assessed and then staffing levels decided from there, but, the people with a vested interest in keeping the wage bill low because they are looking at profits, are usually the ones making those decisions.
Unless it's glaringly obvious that it's unsafe then usually, a home will get away with it as long as nothing goes seriously wrong. I worked somewhere with 2 staff on shift and 16 residents, at least half of those residents needed 2 staff for moving and handling or because they exhibited challenging behaviour, so when both staff are delivering care to one of these residents, there's absolutely no one to respond to other residents, or they do that care on their own as the other person responds to the other residents. Neither is acceptable however with those resources provided, what exactly are the staff to do?
This home was inspected as all are and rated 'good' - staff levels and residents needs via their care plans as well, and it was flagged to managers and had also been raised with the CQC in inspections by staff. So they were aware of staffing levels and residents needs. But it was only when there was a serious incident that suddenly the inspectorate decided that the staffing levels weren't adequate and the care provider told to improve it. Too late by then because someone had already come a cropper over this and the owner & management tried to throw the staff on duty under the bus by insisting they were in the wrong - for once the inspectorate didn't buy it and the real reason was seen.
Horse, bolted and stable door springs to mind though.
In reality most care homes are under staffed as in there aren't enough staff to provide the level of care that's required, and then when those staffing levels fall again because there's a lack of care staff in general and positions are hard to fill and keep filled, well you have the staff that are there fire fighting constantly and responding to each situation as it arises in order of priority, rather than being able to respond to everyone in a timely fashion.
And those, like the OPs aunt, who have people to strongly advocate for them, do usually end up getting better care - but then it's at the expense of someone who doesn't have anyone to complain and kick up a fuss. Because homes don't want complaints so I suspect if OP complains loudly enough, then it'll happen, but not because it could have all along, or because they'll put more staff on, but because a corner will be cut elsewhere.
It's this that pushed me, and others I know out of care. Because we do care but we cannot deliver what's expected because profit is the main driver, not people.