While I can appreciate the gamification aspects of (typically video-game) progression systems, I think it's also important to remember why they were created: to give players the feeling that they're making progress, even when in real-world terms, they're not particularly. i.e. it's about the discrepancy between how quickly a person *actually* improves at a particular skill or activity, and how quickly they *want* to improve at it. Video games are very good at using progression systems to give the player the feeling that they're improving at a faster rate. Honestly, when it comes to sports activities, disc golf actually is a pretty controllable (i.e. easy to learn and get better at) game. New players generally get better quite quickly, thanks to the (initially) relatively small number of techniques necessary to level out a disc's flight and generally aim a throw.
So I definitely wouldn't agree that [new players] "start with everything they need at hole 1", and I think disc golf does a pretty good job already at giving players the feeling of making rapid progress, but I would concede that, like many physical activities, there are definitely plateaus, places where, for a variety of reasons, players essentially stop improving (for at least a while). These are where I think the concept of video game progression systems make the most sense to look at, although again I suspect that with better course design, and requiring the player to learn a greater diversity of skills, we could definitely do a better of job of keeping players from feeling like they've plateau'd without resorting to 'unlockables' or RNG mechanics. i.e. if the one skill that a course is teaching a player is a natural hyzer, they're likely to learn that skill and plateau at it fairly quickly. But if we design courses to test lots of different skills (together and separately), the disconnect between a players' actual skill progress and their desired skill progress could be a lot smaller.