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If a significant bank fails there are no liquid or semi liquid assets, at all. None. A failed bank’s liabilities always outstrip its assets, thanks to gearing.

Any existing shares were pretty much valueless at the point where the bank is prevented from failing, so what you are suggesting mostly happens anyway, except the state takes on only liabilities.

But the banks weren't just underwritten, or given a pile of cash in 2008. They were wholly or majority nationalised, which certainly included less liquid assets, which were eventually sold off. Those that survived were also required to massively restructure to focus on UK retail, de-risk and downsize.

And e.g. Lloyds shares eventually recovered and were sold to recover most (not all) of their state investment.

None of this means I think the situation should have been allowed to occur in the first place, or that penalties shouldn't have been harder, that individuals shouldn't have faced criminal consequences, or that elements of the restructuring weren't mismanaged.