TLDR; the Runescribe was designed to fail.
I’ve only ever played 5th Edition D&D, but I love taking monsters, abilities, feats, spells, whatever have you from earlier editions, and usually that means 3rd and 3.5 (I rarely know which is which when I’m flipping through a supplement).
Back when I was playing my first campaign, the Runescribe came out.
Pretty interesting concept, right? It was to me, a natural fan of Multiclassing who was at that point getting familiar with the downsides of that aspect of the game. I figured something ostensibly designed to help you explore A character concept within Multiclassing would smooth out some of the issues that was previously having with it. I never actually got to play the rune scribe, the concept stuck with me for quite some time. I never really understood why WOTC didn’t revisit the concept in 5th edition.
I began designing some prestige classes of my own, sticking to what I figured was the formula of the prestige class presented. The principles of design were simple:
Where core classes are generalized, and subclasses slightly less so, prestige classes should explore very specific concepts ( people who use shadow magic, mounted combatants, etc.).
Prestige classes should be mechanically dense. Ribbons should be rare, and only ever presented in addition to useful mechanics. Just about each level should provide the player with some new ability, whether active or passive.
Prestige classes should retain some of the limitations that were in mind when Multiclassing was designed. This manifested as setting a lower limit for when the prestige class could be accessed (level 5), and not including any ability score improvements.
I started setting up some polls, surveys, etc. If I wanted this thing to survive play testing, and eventually public release, I needed to know exactly why people disliked prestige classes in earlier editions. I received quite a few preemptive attacks and criticisms. “Why are you doing this, we already have subclasses! Don’t you know subclasses were introduced to replace prestige classes?”
Thank you, NPC! It never occurred to me to research the thing I was designing.
On the other hand, a quite a few people who were excited at the prospect of someone other than WOTC taking a stab at this. I suspect it was were very specific reason; I asked them what they hated most about prestige classes! Genius, I know. The response was nearly universal; “We hate the stupid prerequisites. We hate having to plan out a checklist from levels 1 to 17 just to make sure we can actually use the prestige class.” There were of course other complaints, but they were usually attached to this one.
I went on my way designing, doing quite a bit of play testing with my long-suffering friends at the table. I think it was a few months after I had started my page that Mike Mearls, Matt Colville, Matt Mercer, and Adam Koebel sat down for a chat about the design of the game. They did another one a few weeks later, but that’s besides the point. In one of these chats, the subject of the rune scribe was brought up. Mike shed a bit of light on the prestige class’s failure to become an official product.
Unearthed Arcana materials have a reasonably high bar to be considered for a future product. If I’m correct the threshold hasn’t changed, but nevertheless at the time of the rune scribe’s release, 70% of the follow-up surveys needed to be positive. Obviously it didn’t meet the threshold (this being something like two years after its release), but what I didn’t know was the exact ratio.
The rune scribe had a positive feedback rate of only 30%, also revealed by Mike to be the most unpopular Unearthed Arcana article released to date. 30%! How could it possibly be so low? Take another look at the Runescribe:
See that little section there? Prerequisites! Now, the normal D&D multiclassing rules include prerequisites. Nothing wrong with ‘em; it makes sense that stupid characters can’t take levels in wizard. Fine! We see two such requirements in the rune scribe. We also see the level requirement. Great balance tool for prestige classes! I can compare these abilities to 6+ level abilities, get away with front-loading, etc. There’s a problem; “Complete a special task”. I don’t mind if you and the DM come together when discussing a character and suss out exactly how or why he’s branching out mechanically. I don’t think anyone does; the issue comes in when weird pre-reqs like this get in the way of play, especially when they’re so stupidly designed. Can’t advance in the class without access to a specific NPC? Pardon the french, but fuck that.
So why include it? I have a suspicion; WOTC never wanted prestige classes to be a part of 5e. It’s not like they don’t have their uses. Having now designed several, I can say there are many concepts not served by multiclassing, but too specific to spread out over a 5e sublcass. Even those that could be spread out over a subclass would be better served in a dense, balanced prestige class. I can also say based on the aforementioned qualities, it’s a great template for more narrative focused deviations in the mechanics of a character.
So why wouldn’t they carry it forward? Well, based on the reactions and information I was collecting, WOTC’s prestige classes made a piss-poor impression on their ability to design class deviations. That was rectified with Archetypes and other names for subclasses, but prestige classes still leave a poor taste in the general player body’s mouth. People’s general inability to properly justify their gut reactions is rightly feared; feedback that goes beyond “I don’t like it” becomes increasingly suspect as the length of the complaint goes on. There can still be a justified complaint with the product at hand, but the longer the word count, the greater the chance the author made some glaring error in his complaint (which allows bad developers to dismiss it entirely).
Would you want to re-introduce a mechanic that your player base had no confidence in your ability to design properly (or rejected it as replaceable on the whole) in that kind of market?
I might well self-sabotage the product when I previewed it, and while I’m certain they’d never admit it publicly, I suspect the designers of D&D feel the same way.
This is all assuming the devs have some sort of competence when recognizing their player base’s satisfaction, and would certainly never tease a product touting an almost universally reviled feature.