High damage "always wins" and is a heck of a lot more reliable than a failed save, especially against high-level enemies who typically have Magic Resistance, Legendary resistance and high saving throws. Casters don't have enough spell slots to even get a single fail reliably. Orcus for example rolls saves against spells with advantage and has +8/+5/+10/+13/+15/+7, 3 legendaries and immunity to a bunch of conditions. A 20th level PC only has 4 spell slots 7th level or above. Even with 3 full casters throwing spells at him every round, your chance of landing even one high level save or suck during a combat is low, so if you do manage to do that then IMO the fight should be over.
In 5.5E high-level martials are extremely powerful and reliable in combat. To date the most dominant PC in combat I have seen played in 5.5E was a 20th level single-class Champion. He fought with a Maul doing 4 attacks (8 with action surge) and being able to select one of 4 mastery options on every single hit. The most powerful PC I have played personally is a 12 Fighter/8 Warlock who was doing a lot more with weapons than she was with spells.
This is why when casters get to high level they tend to concentrate on things that buff/protect the party or do damage in boss fights. When it comes to damage casters have some really great AOEs that are situationally awesome and better than anything a martial can do in a round when those situations arise, but they are outclassed by martials most of the time.
You can complain about a lot of things with respect to martials, but as long as you get average rolls on your abilities, martials being weak in a high-level game is not really a thing in 5.5E.