I think the "problem" with Grant and Semi plus a few others from our deep bench is that due injuries and roster weaknesses, they have been being used in roles that are above their pay grade so to speak.
Right now, we have an elite star (Tatum), a star (Brown), a group of starter level players (Walker, Smart, Fournier, Thompson), one new fringe starter (Parker), and a couple of good rotation bench players (Pritchard, RWilliams). All of these nine are the core rotation. They will see regular minutes in the regular season and playoffs.
To me, the next tier that is outside the core rotation can maybe be called long bench. This includes Langford, GWilliams, and Ojeleye. These are players that are proven as legitimate NBA players and can fill in when needed but aren't quite in that core rotation. These are not useless players. In fact they are very useful and every good team needs this type of player. The trick is to have the personnel that allows you to use these players correctly.
Then there is the deep bench. We have a few of these (Nesmith, Edwards, Kornet) as does every team. Ideally, these players are developmental, like Nesmith. You don't expect them to play that much but the hope is they turn into something. Our group, for what they are, is really not that bad. Two-way players are by definition fringe NBA players. They have one foot in the G-League. You can't expect them to be more than that.
With Fournier and Parker added, everything lines up much better. All players can be used at their proper level or below (below meaning having a starter level player like Fournier being used off the bench). No one has to be used above.