Cagayan is not the best first-time players season. It's very good, but there are some flaws (namely that one of the three tribes is absolutely worthless, much like Philippines) that hold it back from being great. Plus, Cagayan comes from a very specific era of the show and I feel like watching it first sets unrealistic expectations for the first 27 seasons (while despite their best efforts to recapture Cagayan's magic, 29-40 fail to varying degrees).
If I were trying to suggest seasons to watch to give an average viewer an idea of what Survivor is as it has evolved overtime, I would say...
Borneo (the first, just to understand the game, plus every additional facet makes this look outdated by comparison, so it's good to watch it fresh and understand that Survivor is a character-driven game)
Australia (I wouldn't normally recommend Australia, because it's not an especially interesting season, but it does establish the gameplay of the first few seasons, building off of Borneo)
Africa (Much like Australia, I wouldn't necessarily recommend Africa, but it is important to understanding the evolution of the game. Plus having the Borneo-Australia-Africa trio establishes the tone of the franchise early on)
Marquesas (Marquesas is an underrated season, and after three seasons of pretty standard gameplay, Marquesas is the first season to start innovating in an interesting fashion.)
Pearl Islands (You could easily say Amazon here, but I feel like anything Amazon does, Pearl Islands does better, and Pearl Islands is just a better season altogether. One of the best, if not THE best season of the show.)
Exile Island (Big skip at this point, but as much as I like them, you can probably skip Vanuatu/Guatemala without missing a whole lot in the franchise as a whole. Exile Island is the next really big evolution of the game with one of its twists, and it has a surprisingly-good cast.)
China (If I really had to trim this list down, it would go Borneo, then Pearl Islands, then China. China is a great season and it's a great example of the near era Survivor entered between seasons 11 and 17.)
Samoa (I would NEVER recommend this season, but it is VASTLY important to understanding the evolution of the show. Survivor has never fully recovered from the lessons learned in Samoa.)
Cagayan (HUGE leap, but much like China, Cagayan is a great season that is emblematic of its era, and it kinda builds off Samoa to really cement the lessons learned there.)
Millennials vs. Gen X (Again, I would never recommend this season. And honestly, I would put Cambodia in this place, but Cambodia's a returnee season, so it's hard to recommend it without recommending a full series watch. But yeah, Millennials vs. Gen X is mostly beloved for some reason, and it, along with Cambodia, pretty much mark the start of Survivor current era.)
David vs. Goliath (It's not perfect, but it's the best season since Kaoh Rong was filmed, and it's the least-flawed modern season, avoiding a lot of the trappings inherent in modern Survivor.)