As an european (Portuguese), this idea of the In-Season Tournament, or NBA Cup, is not new to me, as I'm sure it is also not new to most europeans.
There's headlines going around about players and fans having no clue how it works, but it's in fact pretty straight-forward. In Europe, all major football (soccer) leagues have a domestic tournament with knock-out rounds, that takes place during the season, parallel to the main league (which is similar to the regular season in the NBA). For Portugal it's the Taça de Portugal, for England the FA Cup, for Spain the Copa Del Rey, for France the Coupe de France, and so on.
All the major football countries in Europe have different leagues (different tiers) and a promotion/relegation system to their leagues, meaning that if one team is trash one season, it is relegated to the league below it, with inferior talent. Likewise, if a team on the 2nd best league in England finishes at the top of the standings, gets promoted to the 1st league the following season.
The Leagues (equivalent to the NBA regular season) are all about playing teams on your level for most of the season, keeping things fair and square. Now, cups? Well, they're the total opposite – a chance for crazy matchups, epic spectacles, and maybe even a little David vs. Goliath action. Plus, for the smaller clubs, it's a cash boost when they score a share of the loot from away games against the big shots. Drawing a match against a powerhouse away? It's like hitting the jackpot, even if your odds of moving forward take a hit. Of course, this doesn't happen in the NBA since its a single league with no relegation/promotion, but this was meant as context.
All these tournaments, especially the FA Cup, have greats amount of prestige because they have existed for many years now (the FA Cup was first played during the 1871-1872 season, and the Copa Del Rey in 1903, for instance).
I think that at the moment the In-Season Tournament may feel like a gimmick, something to increase the importance and engagement of the regular season, but I think it has potential to be something embedded in the NBA for years to come, it just takes time (not 152 years, but some time).
King of the Ring is absolutely worthless these days