The issue of the barrier to entering a forum and ask a question used to be a non-issue, as it was easily solved by appending a shout-box to it. Ephemeral, anonymous, low barrier chat coexisted with search engine-indexed, longer-form forum threads (as well as pinned threads that had a similar function to a wiki).
Pseudonyms were less of a problem when you could use a different pseudonym in each forum, while on Discord/Reddit you are mostly confined to a single identity for all forums.
Having a barrier of entry in the form of having to sign up to a custom forum to participate on threads had its problems, but was useful in preventing spam and low-effort content. Most larger Discord servers I've been in try to replicate this property by requiring some sort of authentication for new members to be able to even look at the discussions on most of the channels.
Discord seems to stand on the middle ground between a shout-box, a message board and social media walls: like a shout-box, discussions are ephemeral and non-paginated, and not indexed on the web; like a message board, you can look up older messages; like social media, it nudges you into using a single account for all your different interests. I can see how this combination can work for some people and for some purposes, and I use it myself, but I much prefer the days of message boards and IRC.