I'll be really honest the thing is Sarada and Mitsuki have better stories than Boruto and the creators focus more on Boruto that's what making it hard to watch or read.Pretty much every character in Boruto series have better story than Boruto himself they have better reason to do things they are doing.
I can read 700 chapters if it's on Sarada but Boruto going that far over better characters doesn't make any sense.
What stories do Sarada and Mitsuki actually have at this point?
Sarada's father issues were pretty much oneshotted by the Gaiden arc. The writers could turn to making Sarada take an interest in the Uchiha clan and learning about it's history and what happened to it, but that would ultimately dive into repetitive territory.
Once she finds out about the history of the Uchiha clan, there are a few possible routes she could go down.
1. She could leave the village/turn against it/try to destroy it/ try to launch a coup de tat. This would be repetitive though because we already went down this route with Sasuke (and the police force with the coup thing).
2. She could try and launch a revolution to change the shinobi world. (Already done by Madara, Obito, Sasuke, Nagato, etc...)
What other paths are there for her?
Nobody hates her or targets her for being Uchiha or anything like that.
Even for her hokage goal, that doesn't really encompass a specific plotline or story (not without some kind of adversity that specifically relates to the hero). Naruto had the hatred of the villagers, the akautski targeting him, and his desire to get Sasuke back as plot points that backed up his progression to becoming hokage.
What does Sarada have going for her?
Sarada's progression to becoming hokage would just be her doing her job and being a good shinobi. No specific plot that pertains specifically to Sarada.
In short, Sarada doesn't really have any specific problems/issues that would solidify her as main character material (unlike Naruto and Sasuke who had things like akautski, and avenging clans to deal with).
As for Mitsuki, he has even less going for him. Story wise, his main gimmick is that Boruto is his "sun", but what kind of plot is that supposed to entail?
Aside from that, the writers could have made it so that some people hated him for being Orochimaru's son, but nobody does (not even Konohamaru whose grandfather was killed by Orochimaru).
Say what you want about Boruto's character, but at least Boruto's fate is connected to relatively uncharted territory involving the Otsutsuki. This fate even comes with a never before seen dojutsu and seal. There are hints that the Kara may take an interest in Boruto as well. No matter how you slice it, Boruto's fate drives an actual plot while Sarada and Mitsuki are basically just shinobi for now.