Your points are good, but we can still further argue the subject out based on the context of your narration. In both trading and gambling, we need luck, only that the level of luck we need varies, and that's if we want to view the expression called luck as existing at all. I must say that many times in my trading experience, there are instances that I could truly express that luck was at work for me, so it exists too there. Take, for example, a trader who analysed the market quite well and opened a buy position with 250 pips take profit and 100 pips stop loss. But suddenly, the market started moving against him abnormally without a valid reason, and for this, it (the market) changed the short-term trend to bearish, which is against the position of the traders. After some times of scary movements against the position, the market now almost hit the stop loss having moved 99 pips of it and remaining just 1 pips to hit it and close the position at a loss.
But suddenly the market could not proceed further with just 1 pips to hit the stop loss but just threatened for hours but still couldn't hit the level. Due to this, the trader could have just taken heart and abandoned the trade and closed his gadget believing he had already lost with no more hope. On getting back to the chart after hours of closing the gadget, he now met the trade in huge profits. I see that as luck and something similar had happened to me many times in trading. Also, the sports betting aspect of gambling could be likened to trading. The two are not so strongly the function of luck but expertise. This is especially true if we limit it to the buy/sell in trading and lose/win in gambling. It's the casino aspect of gambling that is so reliant on luck, even though the expertise in trading will still yield better results than the expertise in gambling.
When we want to discuss the context of luck in trading vs gambling, we must bring so many things into bearing and as we go along with the analysis we should have at the back of our mind that luck is a subjective thing, just as skills is subjective, luck don't just happen, you must position yourself for the luck so for that when it comes to trading, luck plays a minimal role and, skills is what have the primary role in trading.
Gambling is based on luck, because there are some games that you pourly depends on luck to win them, most of the times games like spin and dice and even football bets this have been the norm with gambling this is why we have more trust in trading than in gambling and just like I have said before, in gambling you can lose all your money 100% but that is not so in trading because as a leader you already have your stop lose limits and once the market get to that level your trade will just automatic execute and then take a lose at a point.
But we have not seen such happening in gambling unless if you take a cash out and that doesn't come when your games are a loss, there only give a percentage at which you already won, so in all you have to depend on luck at all time because even with your luck you still stand the chances of losing the bets/games most especially on in the house games.