Manbearcat
Legend
Which is fine, as there's some inherent limitations that mean the wizard (or cleric) isn't going to be able to pull it off every time and their being able to pull it off some of the time is quite OK, and is a large part of what makes playing those classes fun.
The limitations:
- the caster's player won't always recognize or realize that the situation could be solved with a particular spell, and-or won't connect the dots to the point of finding that spell in time for it to matter. Usual result: either someone else solves the Obstacle/Problem by other means or it remains unsolved
- the character might not have the key spell prepared, or (less commonly but is still happens) might be in one way or another out of gas, or in some cases might not know the spell at all (e.g. the adventure is written on the assumption someone in the party has Knock as a spell, but no-one does). Usual result: either a delay in solving the Obstacle/Problem until the caster can re-load spells, or it gets solved by other means, or it remains unsolved
- the enemy might take action to prevent the caster from casting, or to interrupt it. In the systems we're talking of, spell interruption is a thing; so a wise enemy might make use of archers or other disruptive effects to hinder casting.
This just reads as "the spellcaster player won't play skillfully." I mean...that's great...unless the player of the spellcaster (and this has certainly been my experience in running AD&D, B/X, and RC) is a highly skillful player! Which is basically the point (as much as anything else). Having an abundance of powerful lines of play is force-multiplied by highly skillful players (which, to no surprise, tend to gravitate toward classes with an abundance of powerful lines of play!).
Personally, I don't often find either of these issues to be a major problem. The game IME isn't as fragile as you seem to be making it out, and frequently has to handle sudden and massive changes in PC power both up and down. Just last night, for example, my party got hit by a couple of lightning bolts and after a series of unfortunate rolls both front-liners now have no armour left! The party's resilience and combat ability just took a serious kick in the you-know-wheres, but the game can handle it without me-as-DM having to change anything about the adventure as written. (whether the PCs can handle it remains to be seen, but the game itself has no problem with it!)
Same thing if they find some really powerful item - almost without exception the game can handle that sudden increase in capability quite well; or so I've found over time, at least.
As for the cognitive-load issue, I figure that just comes with the territory of trying to run high-level games. That said, it's on the players to worry about their characters' items, not on me.![]()
Here is how I'm intending "fragile."
Your B/X Fighter has gained Boots of Levitation and a Sword of Flying! Huzzah! Except...you haven't just increased the lines of play for the Fighter (by giving them Y-axis capabilities) and rendered Flying/falling threats considerably less dangerous (or irrelevant in some cases)! What else have you done?
* You've just force-multiplied the clever Wizard player by increasing their lines of play! Instead of 14 spells with 2 slots typically allocated to Levitate and Fly, you've now freed those slots and responsibility for those lines of play up from the Wizard! Instead of Levitate, they'll now load out the powerful Invisibility or Web or Continual Light! Instead of Fly, they'll now load out the powerful Haste or Fireball or Invisibility 10' Radius!
So falling and flying get nerfed brutally or become irrelevant. We can still obviate or minimize y-axis Obstacles or Pits/Chasms and can access Y-axis opportunities. Light and loading out for it/bearing it now isn't a thing (we'll take Continual Light). We can now ingress and gain surprise/egress from threat/scout like crazy with Invisibility 10' Radius (we'll take that spell). This sort of Daisy Chain when adding a singular item or two to the game is the definition of "fragile." Play becomes an expression of a fault line whereby it becomes increasingly unwieldy in multiple, pivotal, oft-unintended, paradigm-shifting ways on the other side of it.