Altar blessings and desecrations are something of a unique tool for Arelith, being that there are so many deities around, that these altars can be sanctified to literally one of dozens of gods from over a dozen pantheons. Which means you are going to have altars for a lot of different gods that have very few followers and also lots of altars for the main gods.
What we lack, is a more significant way to investigate their damaging and desecration.
Altar Desecration is a glaring hole in the abilities of anyone who tends to the altars of their own god, pantheon or other pantheons and wishes to bring light to damage. As the current status quo is, people can just... walk up and 0 RP desecrate an altar with 0 repercussions beyond a -50% piety cost. It is quick, it is vile, and the altar is left unusable for its intended purposes until repaired which, for some gods... is VERY difficult because of the lack of clerics of that deity about.
Desecrating an altar is an inherently holy/unholy act, and it has lasting impact even after the person does the damage, but the balance of being able to destroy an altars attunement coupled with the relative quickness and inability to investigate means that this is something that can be, and Is abused.
Some things that can help fix this issue and make altar desecration more roleplayable:
Firstly, make altar desecration -investigatable by those with either High Cleric level or Divination. Altar desecration is a holy act, you can't just spill paint on it and make it not talk to god. You are using Divine or Unholy power to taint that altar and disrupt it's connection. This isn't a free action, you're spending quite a lot of peity to do this act. There is no way to NOT leave a piece of yourself behind that a talented or experienced cleric or diviner wouldn't miss. Having the ability to track who has performed a desecration would act as a small stop to those who abuse the system and do fly-by-night desecrations on altars, as well as open the doors for further Roleplay on the subject and encourage in game solutions to be sought other than "Welp... Altars desecrated again. Gotta go get bob and reconsecrate it again.
Second, make the action of desecration take longer. Desecrations take 5 seconds to do. Someone can literally walk up in a quiet moment with noone around, desecrate the altar, and walk away. This is INCREDIBLY unbalanced. Desecration of an altar should take time. You are damaging an severing the connection with someone's god. This should be something that has a timer to perform like a long cast and you have to stand there and dedicate time to perform. This introduces an element of risk for the person performing the desecration by forcing them to stand still unobstructed while performing a -cast or -conjure emote in the air. What if I'm walked in on? What if I'm interrupted? What if someone catches me? These are things that someone desecrating altars SHOULD take into consideration, because as it sits now, someone with a literal quickness to them can just walk up, *boop*! desecrated!.
Third, make the act of desecrating an atlar cost more. Currently it takes 50% of your piety. Piety comes back relatively quickly for some characters, and slowly for others depending on god and actions. Desecrating an altar should take more out of the one performing the desecration than just a bit of their divine connection. Adding additional Piety damage wouldn't really work because as it stands, someone at 50% piety can still desecrate another altar and be good. Having some kind of debuff applied to the priest performing the desecration could work, a bit of divine feedback from the action that stuns/dazes/magically debuffs the character like a death debuff, that can't be removed by magic.