I agree if you look back, you can find out THE World Champion for the era. But they are not Lineal Champions or Undisupted Champions. As for The World Champion of the late 30s/early 40s; history suggests that Steele won The Championship; losing to Apostoli in 38; who lost to Garcia in 39; who lost to Overlin in 40; who lost to Soose in 41. But while reigning, Apostoli lost a fight to Young CorbettIII, in a fight where CorbettIII was under 160lbs. Apostoli did win a rematch for the Championship nine months later.
Sometimes, the "alphabet" holder often does more than many of the unified champs i.e Wilfredo Gomez, Larry Holmes, but it always good to have a unified holder, unfortunately in these wacky times, it's just not going to happen a lot.
If you really, really like the fighter with the splintered title, you can rank him as if he was the undisputed master of the era. Otherwise, it's bad.
In an ideal world the two best fighters in every division would fight each other next week and we'd have 17 ring champions that had prestige because they were ring champions so much so that everyone else wanted to beat the ring champion. The media would denounce the alphabet belts and noone would call themselves a champion unless they beat the ring champion. The ring would then sponsor stonehands awesome work as a "correct lineage". If number 2 don't wanna fight they get dropped in the rankings. As it is and as it has been for a long time in boxing, there isn't that prestige nor drive. I don't look at titles, I just decide who I think is the best title holder per division, be it ring, lineal, alphabet or other (unless we have radical cases like gamboa). That to me means more than anything else. Man beats the man is fine in an ideal world, but in the real world we've ended up with **** like briggs at hw, erdei at lhw, red at ww etc. Lineage only works as long as it's consensus and there's a drive for it. It's currently a mythical title and unless that changes my viewpoint won't change.