I've been picking from a different list (the huge meta-list project from They Shoot Pictures Don't They, which I think does factor in the 1001-films book as one of a whole bunch of things they feed to their Algorithm) but yeah, a lot of the pre-1930 films were a real slog, at least in part. I only bounced off a very few but I was pretty damn bored for long stretches of some others, I think justifiably so.

Big misses for me were anything horror (Nosferatu, The Cabinet of Dr. Caligari—hell, maybe I just don't like German Expressionism?).

Surprise hits were some of the more arthouse films. A Propos de Nice and Man with a Movie Camera were two I loved and are both definitely not conventionally-entertaining. They don't even feature narratives, in any normal sense (but they kinda do?). I also dug some of the Big Damn Movies like Intolerance and Gance's Napoléon—but that wasn't universal, because I found Birth of a Nation unwatchable (I gave it like 90 minutes then bounced—I'd enjoyed none of it, and not just because of the terrible message). Nanook of the North was another surprise hit for me—OK, it's kinda faked or whatever, but they fucking hunted a walrus, for-real, using traditional methods. That they were doing it when they did might have been "fake" because they didn't really do it anymore, but they did it, for-actual-real, which was just nuts to watch, among other things that were "fake" but more-real than a lot of what you might be able to see today.

Archive.org had a large selection of silent films as well.

https://archive.org/details/silent_films?tab=collection