Shelter Scotland Director Alison Watson tells TMZ ... the country's capital should be able to host such a major event without creating a huge impact on the city's homeless population. Alison makes it clear though -- the org has no beef with Taylor.

Instead, she says they're pointing the finger at the "decades of underinvestment in social housing."

Here's the deal ... TS is set to arrive in Edinburgh next week -- playing 3 nights at the Murrayfield Stadium as part of her international tour. The homeless community there, however -- who would've previously been given tourist accommodations as housing -- are now being sent out of the city to make way for the influx of people expected to show.

Of course, understandably, this has left Shelter Scotland very upset ... as they hope this doesn't set a precedent ahead of the city's other big event, the Edinburgh Festival Fringe.

Alison had previously said... "A family going through the trauma of homelessness in Edinburgh should not have to move miles from their job, school, and community to find emergency accommodation."

She added, "At a time when the City of Edinburgh Council has declared a housing emergency and the Scottish Housing Regulator says the city’s homelessness services are experiencing systemic failure, we need a different response from the Scottish Government."

Still, we can't say we're surprised priority is being given to the tourists ... as Swifties are spending money on housing, food and travel -- reportedly giving a "Swift lift" to economies across the globe. Granted, it's still pretty crappy to see that it's happening at all.