It wasn't so much about being good, but I was pitting myself against people who joined the same program, and snowboarded as little as I have. The faster learners were linking turns by the second day, and had far more control than I had on the fifth. Even the slower learners were starting to overtake me in control after the fifth day. And they got tired far less than I did even though fitness wise, I was one of the most active of the group. No one were carving down the slopes, we are all still beginners, but I felt that I was lagging behind the group.
But tightening the boots on the 8th day really made a breakthrough. I am still a beginner and will remain to be one for many season to come *but* suddenly I felt I had control. On the 9th day, I went half a size down (smallest they had) and it got better yet but my heel were lifting a lot and I tired me out. 11th day, I changed resort and went for a really battered traditional lace boots that was another half a size down. The boots looked terrible, but it reduced (but not eliminated) the heel lift it my control was again improved and I could snowboard for hours at a time without my feet killing me.
So yeah as you said, the boots had to be tighter than what I was used to / know is good for me from my hiking experience. With hiking, I had to size up. I learned that going not half, but an entire size up was beneficial for long distance (30+ km) due to the feet swelling after about 20km, and it also provided space for layering when going to colder places. With snowboard, it's completely different, but it was something I had not realised (I've skied/ice-skated for 7 years, but it was a couple of years back so I do not really recall how tight the boots were).
At any rate, yeah, the last five days of snowboarding had been really fun and I am now ready to commit. Hence the decision to invest in boots because drn, those really make a difference!