1. I found the guide a bit too theoretical, and skimming through it I didn't notice it had any info not learned by just playing a lot (experience) and by watching demos, if anyone likes that. In other words I appreciate the effort, but this looks more like an article than a guide.

Duel and videogames in general are mostly situational and of particular knowledge and execution, simple and without much thought and innovation while playing, practical if you want. A non particularly smart kid can be the best in the world in the hardest of videogames, which btw quake is not.
Deliberate practice matters the most, then guidance and videos can be pretty useful if they are specific, gaining the necessary knowledge faster in order to play the game and understand what's going on (spawns, spawn system and such), or put yourself in the mind of the player so there's a different perspective.

2, A generic duel guide should be useful for understanding the gametype, applicable to all of them. That mindset and metagame is not present, for example of not giving things for free, positioning, tradeoffs, weapon ranges, useful rocket jumping, circle of the items, traps, etc; knowing the possibilities and what the gametype is about. I remember some guides like that for q1 and q2.

3. In the end for guides video is always the best way, as this hobby is practical. For example strenx's videos were improvised and everything, but they are miles better than reading the theory of a videogame because they were specific so will mean improvement and more understanding. I still remember some bits of the short aerowalk tutorial, and liked the initial spawn play at dm13.
Also, those should consider the different skill levels. A 1k elo player will not understand something aimed for 2.5k.

4. What I want to say is I would have improved more by spending those 5 minutes in playing than by reading a non-specific "guide" (point 1) that at the same time is not metagame based either (point 2), and to be honest I will forget about this guide in the next 10 minutes whereas I still remember most of the ESL dm6 match (point 3).

5. If anyone wants to make a contribution this way what would be useful right now is not written guides, as there are more than enough written already. What this subgenre still lacks is good video guides for all skill levels, particularly of the highest.