There's a fundamental difference between an issue that is unsolvable due to lack of information and an issue that is low priority.
For issues that are unsolvable because they don't contain appropriate steps to reproduce or known debugging and troubleshooting techniques have not turned up anything, the closest you may come to a resolution is the addition of additional instrumentation for future reports. These should be closed, stating as much. Future reports should include references to the additional instrumentation or better reproduction instructions.
For issues that are reproduceable and solvable, these should not be closed just because they are low priority. From a customer service perspective, it's much better to know that something is a known and understood issue that has been deprioritized than it is to have customers finding issues for the first time. Plus, it improves traceability to all of the instances of the problem for communication and discussion.
Deprioritized issues shouldn't become a "black hole" or a state of "perpetual limbo". They should be regularly triaged. If there's sufficient information, tests should be written and linked to these issues and run from time to time (but not as part of a regular build, since they would be failing tests) - if the test errors or passes, then the situation has changed and perhaps the issue should be revisited to see if it's still relevant. You can also link the issue to various features or functions of your system teams working in relevant areas can find open issues and see if some can't be resolved in their ongoing efforts.
"Won't fix" is, in my opinion, an invalid response to a bug report. It's either not a bug or defect and the system is behaving as intended (although perhaps documentation, training, or something else needs to change so users don't think it's an issue), cannot be reproduced with current knowledge and can be closed if the people experiencing it cannot provide sufficient detail or once some instrumentation is in place, or is a known issue that is just deprioritized.