That's not my intention. I genuinely don't understand your stance and was seeking clarification.
If you sought clarification about my stance, that was definitely not clear in your text. For starters, I didn't see a single question asking me for clarification on my position. There were no questions at all. What I did see was you patronizing me by declaring that it's all the whims of GM and that I would be better served by playing a different game other than D&D. There are definitely more polite ways than that to seek clarification. So please telegraph your intentions more clearly and politely in the future.
Unless your DM is shackled to a pre-written adventure chosen by the players and has no discretion over how it runs (in which case, you probably should be playing a CRPG), everything that could grant XP is at the DM's discretion, just as much as milestone leveling.
Over on the Shadowdark Facebook group, there's a new DM who says he historically will go months between giving out treasure. This is an issue because collecting treasure is how people level in Shadowdark. So the DM fiat means that no one can level unless said DM creates an alternative XP system (which is what they're trying to figure out). But in the end, it's all down to their discretion.
So, back to my confusion: How is milestone leveling worse than getting XP when the DM drops treasure into the game for the player characters to find or puts in fights that the player characters can win? Isn't it all DM fiat?
Here is what I initially said: "Whatever XP is rewarded for, I prefer that it is player facing in the game rules." I don't think that either "good roleplay" or "milestones" constitute player-facing rules for XP and leveling.
If I play video games like Diablo or World or Warcraft, I understand that it's all programmer fiat about when and how I get XP. They can adjust XP and progression rates. They determine what quests and mobs are there as well as their associated XP value. They determine how much XP I need per level. They determine the drop rates for items. I know there are nevertheless player-facing mechanics that let me know the various activities that will provide me with XP: e.g., killing monsters, completing quests, gathering and crafting, resting for bonus XP, or even (unfortunately) spending real world money to buy a level boost. But I don't think that there is not much of a meaningful or substantial argument to be had by reducing all of this to "It's all just programmer fiat."
Gold as a level-up mechanic is player-facing. It tells the player what they must do in play for XP: find gold/treasure. Regardless of whether it's the GM's fiat if gold is or isn't there, the players understand that gold equals XP, so they can set their play goals, activities, and meta-strategies accordingly.
In Dungeon World, players know that if they fail a roll on a Move, then they will get XP. If they do the action in their playbook associated with their chosen alignment, they will get XP. (There are variations of this in other versions of Dungeon World too.) In Free League games, the players know that they will get XP at the end of the session for each of the things they do in the checklist. There may be some discussion at the table about whether what they did applies to the checklist, but they at least understand "do the thing in the game for XP."
In contrast, "good roleplay" is an invisible and arbitrary standard. What is "good" roleplay? What does it look like in the game? Maybe someone genuinely thinks that they did roleplay their character well, but the GM wasn't impressed or they were more interested in their buddy's roleplay, so no XP for you but XP for his bro Chaz. Maybe my roleplay produces two highly different results based on who is the GM. I don't think that "good roleplay" provides a clear and reproducible Skinner Box for player behavior. I think that this often unequally favors certain players over others. Like you get told that you will get promoted at your job for "good work," but you realize that there are no actual metrics for job performance, which becomes increasingly clear when your boss only promotes men, who mostly all went to his old undergrad college or fraternity and show up late and hungover to work, and he never promotes women in the office, no matter how hard-working they are or the results that they achieve.
Likewise milestone leveling is a little too much "you level when I say you level." It may not really matter what the players do. The players have no clear goals that they can pursue for a milestone. What even is a milestone? What does it look like? What is the metric? If the GM didn't declare that they leveled, how would they know that they had achieved one? It's just when the GM says, and those standards are very often unclear as a player. So a lot of milestone play, IME, devolves into players sitting in the backseat of the car wearing blindfolds repeately asking the GM, "Are we there yet?" Again, there is no real Skinner Box for players to pursue their goals.
In contrast, Shadow of the Demon Lord does have a quasi-milestone system, but it's player-facing: you level up when you complete a tier-appropriate adventure. So I know that I have to complete the adventure if I want to level, and I won't get a level beforehand. I'm okay with that.
