Shirou was stuck with one servant, and Shirou is a discount magus and master himself to the point Artoria significantly underperforms due to him being a low-quality magus. Shirou himself survived similarly to the FGO protagonist by circumstances panning out (if the player makes wrong choices, they easily end up with him dead due to how at a disadvantage he is under that situation).
I'm not downplaying anything. I'm stating factual information that refutes your narrative. Daybit makes it clear as day that he is fighting with you as a master, not a crypter; this is explicitly stated by Daybit (so when Daybit says no holding back means as a master not as combatant). This is set up as a master vs. master duel to test who is the better master, and since Daybit has just an excellent single servant, no to little experience as a master (he completed the Temple of Time Crisis simulation by himself without servants), due to an incident from his childhood he couldn't summon servants, and when he did summon Tezcatlipoca due to special circumstances, he outright states he has little to no control over him and he just does whatever he wants. Much of Daybit's efforts are dedicated to working (mostly solo) to awaken Ort and let alone the fact that Daybit can only remember 5 minutes of each day, meaning given he was gathering info about how to stop Ort, even if he commanded Tezcatlipoca as master, his learning would be significantly impaired due to this. In addition to that Daybit is capable of summoning quite powerful creatures from beyond of universe (not servants) due to accident with alien artifact and does so in chapter 19, he doesn't do that during that fight since he is fighting you as a master (which further evidences. So fight is about you competing with daybit as masters, not you competing with Tezcatlipoca as combatant). In fact Tezcatlipoca already fought you as combatant and he demolished protagonist + mash and allies to the point they were unable to even harm him due to his ability, U-olga Marie had to save him. Tezcatlipoca was fighting in last fight as Daybit servant not as independent combatant (which similarly to duel as masters with Yu Mei in her interlude where she loses to protagonist with entire team of servants including high tiers like Mordred against single servant due to how poor she is at tactics).
