I have actually wanted to make a thread on this (and some other things) for a while since the comparison comes up so often. I really disagree with what I'm reading as the general sentiment of Elden Ring as better than BotW. I'm really enjoying Elden Ring but it's actually making me appreciate some of the more controversial design decisions in BotW. For example, there are a lot of people who complain about replacing long, complex dungeons in Zelda with the piecemeal shrines and just the four limited size divine beast dungeons plus Hyrule Castle (and technically the four are optional as are most shrines.) I never agreed with this argument but playing Elden Ring has helped me see why. Landscape puzzles and then small site specific puzzles/challenges are much more consonant with the 'go anywhere/do anything/all bets are off' open world design that BotW had and I think ER is going for. ER shines in many places when it plays like this and then its like it reverts when you hit one of the big legacy dungeons or whatever. These tear that above spirit completely out and its like your thrown back into a different game. I now see why the BotW team went with the decision to basically excise / minimize dungeons and spread puzzles throughout the open world. I wish ER was much more like that.
Relatedly, especially in dungeons From "puzzles" aren't really puzzles. Like you have six ledges you can hop off and only 1 is really 'the right' one is just dumb trial and error and its very grating. (Again, I'm loving Elden Ring but these are the things that stand out in the comparison.) Whereas in BotW even for some of the hardest puzzles, there is a logic to it; the game doesn't tell you what to do - in this way they are very similar - but it is designed such that if you really examine your tools and the environment and what is being asked of you, you can figure out a genuine puzzle with patience and inquiry as opposed to either brute trial and error or googling. Interestingly, the really tough fights in ER are puzzles in that manner. You might have to do them several times but there's usually some strategies and tricks that you can work out. So I know ER could be more like that and am disappointed it is not.
Finally, while ER is lore heavy to say the least and full of just fantastical ideas and concepts, both games are fairly narratively simple unless you're really digging in. However, for all the freedom that ER provides, whenever you essentially cross one of the storylines in progress or encounter a new NPC, it again feels like you're tripping over a very weird, very invisible, and very inscrutable straight line in what is supposed to be an open-ended game. There is no amount of lore reading that could guide you through those long complex storylines; you basically have to use a guide (even the in-game messages hardly suffice.) And this too breaks the magic or what not of that really no-holds-barred-openness that both games are clearly going for. It further makes it feel (I'm not saying it is like this, but rather it engenders the feeling) that there really is a "right way" or several "right ways." One of the unsung/undersung achievements of BotW is that it never felt that way. You could just completely go off after the intro and genuinely do your adventure and it would only be in discussion with others, videos, etc. that you'd see how wildly different people's playthroughs were. I think this is trade off and no one has yet solved it. (To throw another game in the mix, I recently finished Horizon FW and they did some marvelous work to make the side narratives line up with the main narrative but by the end it really comes off the wheels if you like are going back to knock off some sidequest you ignored earlier; it just doesn't make narrative sense and is a bit jarring despite how much care they clearly put into the storytelling.) The BotW solution to this was simply that the narrative is so suggestive and the side bits so discontinuous that basically that jarring feeling never occurred. I think there's got to be a way to do more but being pretty far into ER I will say the ER method does worse (although with more.)
Basically, long story short (and I could go on, there's a lot of stuff): I wish ER had broken with the Souls past more thoroughly just as BotW did with the Ocarina of Time and all 3d Zeldas after formula. Not to ditch what is amazing but to genuinely go all in on something pretty new. BotW still feels new and as people have said here, that's despite it being quite old (at least in video game terms) at this point.