ranting on discord, copying it here:

B/X is a broken as fuck system. It wasn’t written with an eye towards what plays well, but what reads well. It’s a simplified version of OD&D that tosses out a lot of nuance that makes that game playable. It also contains a mishmash of AD&D elements. “Playtesting”, in regards to BX, is a joke concept.
It’s also a very limited system. BX advertises 14 levels but in reality games fizzle out between levels 6-9, because there isn’t much to do beyond delve into dungeons and travel in between dungeons. BX has wilderness encounters numbering in the 100’s of monsters, but no method to resolve combat at that scale. In OD&D it’s assumed that you would play out the battle using miniatures and the Chainmail rules, BX has no replacement system and no mention of Chainmail. BX mentions the creation of strongholds, but no details on how to do so, what their purpose is, or how to manage them. Even AD&D describes how strongholds can manage henchman and followers.
There’s a reason BX “hacks” and supplements are so popular: you simply need more rules, if you want to play a game that’s more than dungeon crawling with 7 character types. Not “classes”, BX actually just gives you 7 characters that you can modify cosmetically and just play

2e isn’t for everyone. 2e is a fantasy world simulator, and in my very biased opinion, it’s the best at that task. It creates a fantastical world that runs on something approaching real world logic, and gives you the opportunity to run any fantasy in that world. With only some tweaks you can use it to run things wildly different than the standard setting, for example Dark Sun, Ravenloft, Spelljammer.
2e is a very expansive game, with a lot of rules. It’s not as rules heavy as 3e or even 1e, but it has a supplement for seemingly everything. The core 2e books are intentionally a reaction against 1e’s heavy handed authoritarian style, and presents most of the rules as options that you could slot into your campaign. The thing I don’t like about them though is the writing style and organization. The split between DMG and PHB was a mistake
Mostly, 2e cleans up 1e, fixes most of the obvious contradictions and ambiguities, and presents a core game that runs really well as a light system if you don’t use any optional rules, or a fully simulationist system if you do.
Unfortunately the greatest drawback of 2e is the ‘90s and the TTRPG community at the time. They wanted rules for everything, heavy simulationist approaches, the option to chuck dice at all times, at the cost of imagination. 2e splats followed some very bad trends that eventually left the game abandoned for trendier games like World of Darkness or GURPS. the “rules for everything” approach reached its apotheosis in 3rd edition, which is when everyone realized that it was a bad idea
Though, as a point in its favor, 2e actually has two (three?) mass combat systems, and at least one of them, Battle System, is actually very good. As a result of the splatbook explosion, 2e allows you to play a full game from lowly dungeon delver to domain ruler to Planescape jumper with plenty of official support. BECMI is the only other TSR edition that does that