There are very few possibility of skill based gambling like I am aware, only sports betting a skill-based a gambling and it is relatively profitable compared to trading.
Altcoin trading is pure gambling whereas skill-based a gambling is are completely consistent for profit making. I will never recommend altcoin trading to anyone as it is more risky at the same time even I am making profits with the skill-based the gambling I'm not recommending it to anyone due to the reason of they might get into vulnerable to addictions.
You are right, people will not stick only with skill based a gambling once they start earning profits from gambling, they will get greedy and will try some other gambling like luck-based one also. But it is their own responsibility and there will be no wrong if you are suggesting people to go for skill based a gambling only after learning required skills.