You don't understand where AS-400 real power comes from. DB integrated directly into filesystem, you optimize your work for how the whole system has been designed and get massive benefits and robustness.

Performance between junior basic code and heavily optimized complex queries even on just Oracle can be 1000x easily, just ask any data warehouse guy (seen it few times myself even though I don't do warehouses). You can maybe add another 0 for AS-400 there in extreme cases.

Yes if you end up doing things wrong and expect that CPU to do some heavy math then yes this will be dusted quickly. Otherwise, not so much.

But this goes against most modern 'SV principles' so I don't expect much love from younger generations here. Business love that though, and secretly wish all IT could be as reliable and predictable as them although that ship has sailed long time ago. One of those 'they don't do them like good old times anymore'.