The alternative is to continue with a process that’s been demonstrably successful, despite it offending your sensibilities.
Banks are prepared to pay for it. People are prepared to do it. It meets the business needs. Change is massively high-risk in a hugely conservative industry.
I think you vastly overestimate the separability of these systems.
Picture 10,000 lines of code in one method, with a history of multiple decades.
Now picture that that method has buried in it, complex interactions with another method of similar size, which is triggered via an obscure side-effect.
Picture whole teams of developers adding to this on a daily basis in realtime.
There is no “meaningful progress” to be made here. It may offend your aesthetic sense, but it’s just the reality of doing business.
(I’m also a fan of rebasing; but I also like to land commits that perform a logical and separable chunk of work, because I like history to have decent narrative flow.)
I had a small X.25 network as combination coffee-table and space-heater at one point; this was before most homes had internet. It almost cost me a divorce.
Doesn’t need to be a “traditional” container. Modulo noisy-neighbour issues, wasm sandboxing could potentially offer an order of magnitude better density (depending on what you’re running; this might be more suited to specific tasks than providing a substrate for a general-purpose conpute service).