I would like to join in the complaining. Some of the other adult interactive fiction sites need an account to post but I can't think of another where you need one to even view. I can only imagine the number of episodes posted will fall off a cliff (admittedly some of which won't be missed).
I don't do it for the 'views' or recognition (I don't even sign my episodes), but I certainly feel less inclined to spend the considerable amount of time and effort it takes to write an episode knowing it could only even potentially reach a handful of people.
Yes, CYOC is there if you still want somewhere you don't need to login to submit, though I generally find the quality is worse than here and some of the content extremely questionable. chyoa is much better in quality, probably because you need an account to write, but it does get new content as people can see it's not dead. It doesn't have the nice fact of technically all branching from one tree, rather being split into stories. (I know technically pretty much no-one actually starts at the beginning, but it's a nice concept.) I also echo Post-Bop about liking the community here.
If you don't want to have things free to read but login to write, I have some other ideas for compromise:
1 - Limit accessibility tools. This is what chyoa does. You can browse and read without login, but the extremely useful 'storyline tree' view, the ability to favorite/bookmark authors and episodes, the ability to change colours (for example to a white text on black night mode) and probably some other stuff is locked behind logging in.
For the UBEA, you could make it so the only places you can access are the recent episodes page (with recent comments, perhaps minus tags) and the very beginning (link to ep 02 - Jim wakes up). Keep it so Google only works if you're logged in (or just add the search). The index, author/tag pages etc are locked off. Maybe commenting is too, though I'd prefer not.
This way rando anons can get a taste of what's available and perhaps be persuaded to start an account, while regular users can nip in and check what's new, whether anyone's followed up or commented on their episodes without the faff of having to log in every time, while still needing an account if they want to write or dig up old favourites (much less frequent occurrences).
2 - Extremely overzelous autocensoring. If the problem is adult content not behind a login wall, then maybe an autocensor? Hear me out. When not logged in, censor everything sexy, not just swearing (so butt, breasts, ass etc). Use ***s or the same word every time (e.g. 'CLOWNS') so people can't just copy/paste episodes into word and find/replace.
New users can pick up the general quality of episodes, see the amount and variety of them, and from context get an idea of the fetish content, the shape of a sex scene etc, ("She groaned throatily in CLOWNS as her hands caressed her swelling CLOWNS, her CLOWNS dripping with desire.") and hopefully think "Man, that looked like it would be hot if it wasn't for all those clowns. I should make an account, it's free."
Regular users will still be able to call in at the recents quickly and easily to see if there's anything that interests them that they'll bother to log in and look at in full, either then and there or later. As above, they could check quickly whether anyone's followed up an episode and if they had read the censored version could start thinking about where they want to take the story. They could also read/check comments.
3 - Character limits. If you aren't logged in, you can only see the first 750, 1000 etc characters of an episode. Like all the above, randos get a taste and are enticed to more, veterans can do the daily ritual of checking the recents/comments and then log in if they see a storyline they're following/author they like has updated.
4 - A mix of two or more of the above
i hope you're open to at least a little compromise, as like many here I cannot see the addventure surviving in a viable form if regulars can go elsewhere to peruse without logging in and randos cannot see the thing at all.