Only today are INDIVIDUAL Diesels reaching the same power levels at was routine in steam days. It just couldn't be done with the technology of the 40's, 50's, and 60's. The attempt to do so, back then, lead to huge electro-mechanical monstrosities with multiple engines and abominable reliability (Centipedes, U50B & U50C locos, C855's, etc.). Even EMD got sucked into this mess, with the DD-35 and DDA40X models. Even the twin engined passenger Diesels like the EMD E-units were proportionally troublesome. All are long gone, except for museums and a very few still in special service (executive trains, etc.).
Very good point, as in the early 50's it took 4 F-7's to do the same pulling as one late Cab Forward (AC-7/12). Even the Under Pants railroad got rid of their DD-40X's or whatever they were.......... Yeah but real locomotives boil water to run..........as long as I live and I model, steam will be the predominate power on my road. Those "maintenance problem steamers" kept a myriad of SKILLED CRAFTSMEN, working. I think the only place where diesels were equal to steam in the early days were the switchers. From the conversations I have had with RR people over the years most agreed that an 0-6-0 could out do a 600HP DE switcher and an 0-8-0 could out do 1000HP DE switcher. But they all thought that it was a close comparison.