Or just consider that sort of Warding/Binding ritual as Conjuring a Zone.
Oh look, Dispel Magic works now.
I'd possibly make it so the PC had to do an Arcana check, taking maybe an hour of study to correctly identify the Conjuration/Zone effect before being able to target it properly with Dispel Magic if I didn't want it dropped instantly by a good roll.
TBH all magic should have a dispel/curcumvent method. As WotC haven't made an "Undo Ritual" ritual I'd use Dispel Magic as a means for stopping long standing rituals in an area (as they sound like a Zone to me). Could also handwave it as short term dispelling as it isn't truely a Zone you are targetting (so you have 5-10 minutes to play with then you are going to need to deal with it again).
IMO rituals are cool. They don't break the game - as they take a long time, burn a lot of cash, and can only be powergamed if your DM is being stupid (Tarrasque in a Lvl 10 game = stupid, or intended to be bypassed like this, at which point it isn't powergaming).*
They are a good way of giving characters some nice "think about it and we might have a way around this" options. Some are a bit vague, but common sense and care generally fix this (and who wants rituals that take 20 minutes to read?)
*As someone said, a Lvl 30 Minion in a Lvl 5 game is just as abusable, as a party of players may well be able to prep, buff, ambush and kill it for insane XP if given the hour or so a ritual needs. In fact, Stinking Cloud + go first = win. Minion starts its turn in the effect = dies. It's the DM's job to stop this stupidity not the PC's, or WotC's.