Since all the data generation and validation is handled server-side, there are very few ways for a glitch or exploit to occur
This means c with Undying all combo really well with cards that put -1/-1 counters on them, because (somewhat counterintuitively) +1/+1 counters and -1/-1 counters cancel each other out
Since then, weve had a few good ritual decks like Nekroz, and players generally recognize Rituals as a solid deck with exception, of course, to Hungry Burger
If sideboards were allowed, it certainly belongs there, but it does not belong in the main deck in my opinion
How much does Drawbread cost
The fact you have to have this on the field means youre ripe for getting messed with before your upkeep, so having spells that give it flash, or drawing that 13th card on the end step before your turn (more on those later)