Hey NolanAlighieri, thanks for playing the game and taking the time to leave a review!
I watched your Youtube playthrough video and had a few good laughs out of it. There were several valid points made on the flaws of the game, and I do acknowledge that the game is far from polished in many aspects. Anyway, I would like to try to shed some light on some of the game mechanics and design choices made from a dev perspective, hopefully that can bring about some clarity to your player experience and make a little more sense out of everything (I won't be able to address everything as the list is pretty long).
▶ About the Lumentite Artefacts dealing 9999 damage
The infographic suggests that certain artefacts can potentially deal 9999 damage in the late game and is not specifically referring to the Woodcutter's Ax (which would be completely busted if that were the case).
The Woodcutter's Ax is an artefact designed to aid the players in taking down the Ravenclaws (the black crow monsters) as those enemies have a high evasion rate. There are many mechanics in terms of damage types that are not yet explained in the demo, but to expand a little further on this subject, you have your standard elemental weaknesses and then there's Absolute damage. Absolute damage is a certain hit type of damage that bypasses evasion and any DEF/M.DEF (except when guarded due to how guarding works in RPGMaker). E.g. if it indicates an Absolute damage of 500, the net damage value will be exactly 500. So while the damage is comparatively low to say a fire-type magic spell used against an enemy weak against fire, it can be situationally effective in cases where monsters have exceptionally high defense/magic immunity/evasion.
▶ About Magic being stronger than Tech
Magic is designed to be powerful in this game, but does not scale as well as Tech abilities. The demo is adjusted to be reasonably easy, to account for players who may be completely new to JRPGs. As such, most of the enemies including the first boss you face are weak against fire-type attacks (which explains why Ignis' Faerie Blaze deals so much damage). Ignis is kind of a glass cannon anyway, with very low HP and defense.
In the video, the gameplay stops before the airship exploration, which is where most of the customization takes place. The game gives the player the option of deciding who will be the damage dealer/healer/tank through allocating stats (Airship Bar) and assigning patches. Patches in the later part of the game will also change how quickly TP is gained. Combined with S-grade artefacts, Tech skills will unquestionably out-damage Magic skills in the later part of the game (It is possible to cheese through bosses by exploiting S-grade artefacts and Tech skills combined).
Do try out the rest of the demo if you are interested, I'll be happy to watch another video review of it!
(One minor thing to point out, Eva's Flash Edge actually deals 3 hits instead of 2 (timestamp 3:27:30 in the video 😅)