I haven't read the novels unfortunately, so I have no way to compare personally.

I'm a huge fan of both books and animated shows, but in the case of this show, I ended up watching it first before I even knew there was a book series.

I do agree that the animated versions of a good book series don't always measure up. But at the same time, I try to give them some leeway, because I know that some things don't translate as well for general audience.

I'm no expert but, it seems to happen to manga all the time too. Though I'm more of a casual manga reader, not a dedicated one. Free manga is hard to pass up lol.

"TSUKIMICHI -Moonlit Fantasy" the anime is a prime example of a manga I read briefly, but ended up stopping since it diverged from the anime and I didn't want to spoil the anime for myself, since it's airing this season. Lots of material were dropped and I could see why. I mean 20 or so minutes per episode is not a lot of time to squeeze in everything the author may want. Plus, the episodes in this case wouldn't make sense if they put in everything, since the manga is more explicit. I imagine that would have changed the tone of the anime big time.

Maybe Redwall series faced its own version of restrictions, both for time and content? Did they explain the reasons for the changes at any point?

While I love anime and animated series in general, I'll always be a book lover first. But I try not to compare the two too much, it's way too easy to get disappointed, just the way you felt.

The Wheel of Time TV series is one such I'm dreading to watch for example. Because I can't imagine how they're going to translate such a huge story into such a tiny time frame a TV show will have.

Books allow us to use our imagination to see the world the author created, but animated shows while enjoyable, doesn't need that part of our brain as much. :)
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the audiobooks are great, you'll also find it printed and as e-book.
Moss is probably a better mice game than the Redwall ones, listening to the reviews, but I haven't played them yet. And I'm hoping hard for the continuation of the tale of Tilo.
https://www.gog.com/wishlist/games/moss
https://www.youtube.com/watch?v=eC3typSPxJ4
https://www.youtube.com/watch?v=clbWMpH9lMg

since this has sort of derailed into "here's a bunch of other stuff you may enjoy featuring mice and the like" - and since redwall's come up a /lot/ in this thread, here's a couple of other things to look out for in a similar vein:

small saga [which now has a wishlist page on the other store]:
https://www.kickstarter.com/projects/sketchyjeremy/small-saga

and
mice and mystics - a co-operative board game where you're mice loyal to your king:
https://boardgamegeek.com/boardgame/124708/mice-and-mystics

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i'm VERY curious about small saga [and i hope, in particular, that that developer reaches out to gog, so that their game can come here, too.]

Yeah but the way the trailer depict itself it felt like they trying to be like Game of Thrones but with anthromorphic animals. Even though the idea of Disney Robin Hood turn into GoT sounds like a very good idea.