I agree incompletely but would extend it to fluff spells like druidcraft magehand thaumaturgy & prestidigitation as well unless they can somehow make those good enough to stand alongside firebolt toll the dead guidance chilltouch ray of frost frostbite etc or even a questionable one like the currently awful truestrike.Fun fact: Shadow of the Demon Lord, a D&D adjacent game, indeed give the equivalent of of Guidance to 1) the Priest (aka the Cleric), and 2) to the Witch (warlock/druid mix) as a class feature called ''Prayer'' for the Priest and ''Guidance'' for the Witch. It works more like the improved Helpful feature of the Expert sidekick class in 5e, where you add a bonus 1d6 to the Help action, and later can add it instead to the damage if the Help action was used for an attack. It allows such characters to lean in on the support role turn after turn without needing spells should they want to do it.
I'd suggest giving ''must have spells'' as features for such classes: guidance for clerics, hex for warlocks and mark for rangers. Making those spells was a mistake, IMHO, because they become poachable by many other ways for other classes that can benefit even more from said bonus.
it's not much of a restriction no, but being on a list where you pick 2-3 from a larger list containing 2-3 worthwhile options pretty much makes it a class feature they need to buy at the cost of cutting off access to fluff spells. If guidance were on the wizard cantrip list where you have a large number of solid options it would be rather different even if it didn't get copied to the wizard's kid brothers warlock & sorcerer alongside the scorlock class featuresIn my campaigns, our cleric had it, our druid had it, all bar one of our four warlocks had it, one of our three bards had it, and a character who gained it through Magic Initiate had it. Thus, in my experience, the fact that it is only on the cleric and druid lists has not been much of a restriction.