There are four reasons mass market things could be not intended to be accessible for casual players.
- They physically can't be simplified without taking away core elements from non casuals
- The target market is a very specific group
- The designer lacked either the time or the skill to make it accessible
- Deliberate gatekeeping
I am not advocating that the experiences of the other players at the table be downgraded. The existing classes can stay unchanged. This isn't GURPS or Champions where everyone is playing by the same rules. Instead it's Draw Steel where the pitch is that every class has a "different" resource. And e.g. "add the round number to your damage" would fit the premise.
The very specific group being targeted according to isn't " Those people who like tactical RPGs" but "people whose RPG group consists exclusively of those who enjoy tactical RPGs" rather than anything that's a friend group first who turn up to have fun with their friends. In an RPG group of four of whom three are tactical role players who would love Draw Steel and the t fourth is a friend of all of them I'm going to recommend either PF2e or even Daggerheart (which is not a tactical RPG but has enough to sink teeth into) or Dragonbane all because of the purity of design. (Valuing purity of design as an abstract good rather than necessary flaw when trying to deal with groups is one of my beefs with Ron Edwards; he considered it incoherent rather than flexible).
And for the record I can think of multiple groups including both my current group and my longest lasting home group where many of the players including me would have been suited to what Draw Steel does well but others would not. I can therefore only see this as bad design or deliberate gatekeeping.