It's the opposite. Reconciliation lets you pass bills that only change spending/revenues, and isn't allowed to change policies which are revenue-neutral.
You might be thinking of how it's not allowed to create a deficit after 10 years, but that's traditionally done by just saying "everything here expires after 10 years" and then leaning on a later congress to extend it.
That still doesn't explain how the OBBBA passed but they can't use the same process to pass a debt limit increase. Do republicans want to add more stuff to the bill? Based on the wikipedia article it looks like it should be able to pass a bill that only raises the debt limit through reconciliation?
They could have raised the debt limit through reconciliation, but this shutdown isn't about the debt limit. This is literally the bill saying what the budget for the next year is, without which the government isn't allowed to spend any money (as opposed to not having any money to spend when it's the debt limit).
I think the reason they can't use reconciliation for this is that the budget has to include discretionary spending, and reconciliation is only allowed to be used for mandatory spending.
You might be thinking of how it's not allowed to create a deficit after 10 years, but that's traditionally done by just saying "everything here expires after 10 years" and then leaning on a later congress to extend it.
(It's a little more complicated, but https://en.wikipedia.org/wiki/Reconciliation_(United_States_... covers it.)