I strongly agree. While I did not look into any problems concerning instance admins (= I'm unable to comment on the issue), I have noticed that Lemmy is a beast of an echo chamber. I don't think this is a direct goal of many Lemmy users, but simply a result of multiple factors:

• Lemmy is FOSS software/ pro-privacy etc. and has a higher barrier of entry; this is probably why Lemmy is full of techies
• The architecture of the Fediverse appeals to many who are against the idea of a single entity being in control; this (and other factors) might cause the high amount of left/ far-left people on Lemmy (e.g. the Lemmy devs are openly on the far-left spectrum)

However, there are many Lemmings that I have seen actively pointing out these phenomenons and criticizing these developments (usually with mixed reactions). I believe that everyone (especially the Fediverse itself) benefits from an actively diverse Fediverse/ Lemmy. Lemmings from all (political) backgrounds should consider promoting Lemmy to communities that are on the other side of the spectrum as well, if they believe in the benefits of diversity. I often read posts about how nice Lemmy used to be before Redditors migrated, but I don't think that the simple kindness/ enthusiasm has vanished yet.

Echo chambers don't protect anybody, they poison any beliefs and hurt whoever is in them; if people don't realize this, the Fediverse is set up to fail from the start. Personally, Lemmy has driven me away from using social media (of any kind) at all (which is a good thing tbh). No social media might be better than decentralized social media after all.