Please implement something to teach players how to play

[Shurrikhan]

optional bonus objectives

See ARR dungeon pathing controversy.

speed bonuses

See the prior pages in this very thread.

Or like optional bonus bosses that may have some extra mechanic or something.

See dungeon pathing controversy in general. Perhaps if roulette rewards were removed, thus taking away the incentive to almost always skip these optional bosses, this could work, but this kind of thing has long been tried and, at least among other daily/weekly/once-per-run bonus systems, has almost never been a success.