Again, we lose because it is scripted to be that way. It wouldn't matter if we were level 70 as well; the devs would still find a way to script that fight so we lose. We could even be strong enough to get Zenos down to 0.1%, and then he will bust out some overpowered move, and we lose. They could also design an even level match so Zenos has a ridiculous amount of defense, basically mimicking what happens at the Reach where we can't scratch him, and we lose. I just don't follow why this even matters. You say the fight lacked oof, and I don't follow here either. The WoL was humiliated among the few who survived the onslaught. They are forced to redraw plans to liberate Ala Mhigo, and the Scions totally get the hell out of dodge, and flee the whole continent. Zenos almost orchestrated a no-hitter, but didn't follow through with a clutch kill.
After finally hitting 70 (if we want to use levels), we have three fights against Zenos we can actually lose via duty failure, so it is not scripted. Few will actually wipe to dungeon Zenos, but it is possible; Shinryu and Elidizenos. You're getting what you're asking for but your response is, "they're lackluster." So if there's no pleasing you, or if it extremely difficult to do so, then I dunno. There just seems to be a lot of bias on your part.
How are you not feeling it when you're previous BiS i270 shire gear that you destroyed Alexander with isn't even phasing him? Because he's 10 levels above you? No matter how you want to look at it, he is more powerful than you at this point, and your character getting to the point that they are able to contest with Zenos should be all that you need to know that your character has grown in experience, knowledge, abilities, and also power. It's how it's done in literally every RPG out there.snippy 2
The lore is filled with clues to how the WoL is getting stronger during SB. The Kojin Blessing; acquiring your Yol mount, and the defeat of Omega is very much canon. If we want to use an ShB example that shows this growth, there is early ShB where the Fauth attempt to make you one of them, and are unaware that you cannot drown. While I also wish it would show our WoL being all awesome powerful in cutscenes, this among many things about your character require you to stretch your own imagination a bit. Besides, when NPCs show their abilities in cutscenes, they don't really display anything greater than what we're capable of with our own skillset. We have some crazy powerful abilities, can traverse between two worlds, and are canonically stated to be a match for Zenos (when not falling asleep in battle anyway).
You also get a display via the echo from Fordola of yourself on the battle field kicking arse using some crazy shizz, so there's that too.