I respectfully disagree.

Lemmy users should have been allowed to choose seeing content from other link aggregators like Reddit, Hacker News, etc.

I do not assume to talk on behalf of the developer, but I would think that that is not the point of Lemmy. Lemmy is supposed to be a link aggregator-slash-discussion platform that is not owned by a corporate entity.

Again, I may be wrong. Please feel free to correct me.

LibReddit users should have been allowed to participate instead of just reading.

That would entirely undo the privacy features of libreddit. AFAIK it was a deliberate decision to disable logins. If you still have the urge to respond in a thread, there is a direct link to the discussion on the Reddit site.

Which is why I think that Lemmy and LibReddit should have been the same project. Instead users who don’t want to compromise have to use both.

Since both Lemmy and Reddit have publicly available APIs, you could consider rolling your own aggregator. I agree with @victorvelsol@lemmy.ml that managing the accounts would pose some challenges.