The financials aren't great - but I don't think some of what you say is accurate. Several airlines managed to secure long-term leases at very low rates during Covid and still have more than a few years to run on leases at those favourable rentals. I think you'll find Emerald is one of them, so although overall cost inflation on things like handling and nav charges will be impacting, ATR aircraft leases will not be hurting. And for the Aer Lingus franchise, it was always going to be the case that the operator would have to recognise unions.
One operator before has failed as an EI franchise (Stobart). It failed pretty much only because it sold and leased back ATR72s at a huge lease rental to allow its then-shareholder to take cash out of the business as a dividend. When those huge lease rates couldn't continue be paid, it all went horribly wrong very quickly.
That is not the case for the current or any future Aer Lingus Regional franchise carrier, so this is not an inherently "bust" business model as you claim. You do seem to enjoy prophesising the demise of regional airlines, but it seems to be heavily from a position of ignorance of the facts.