Updates break mods. Games get constantly updated. We can’t really escape these two facts.
Single player modding could still be possible in these conditions. Just have to turn off updates and play offline or over tcp/ip, like in Diablo 2.
By adding the 30 day login requirement Blizzard effectively makes mods impossible. I wonder if that can be considered false advertising.
For real? CASC no longer works? Well shiee, it seems the devs pulled a bait & switch then. This is a perfect example why I detest DRM such as this, or always online. Modded single player was the big selling point for me as well.
Or better Yet… do as I did…
take the matter into your own hands and adapt the mods you use by yourself…
I did this with full merc equip for 2.4 ( not sure if it still works with 2.4.3 but it’s worth a try).
originally full merc equip for D2R in patch 2.4, CTD’ed whenever right clicking the merc’s portrait… after looking “under the mod’s hood” so to speak You begin to realise why.
Esentially it’s mostly about .txt files and their newly added columns, that’s easy to work around with d2excel, also there are other text files also written in plain text that don’t reqire d2excel but are mandatory to be updated because they make the game work in new engine. although i still haven’t figured how to properly align the extra item icons in legacy mode, however in 3d FullHD resolution everything worked fine for 2.4 after I was done with it.
Unfortuneatly I’m not able to play the game during summer, It’s going to become intensively hot afer I launch this game in a matter of minutes, and I have no AC, nor am I in position to install one. Currently I’m unable to check if my adaptations will work for 2.4.3 however back in 2.4 they worked just fine.
TL : DR
there’s a third option= start using your brain and adapt those mods You’re using by yourself
there are other methods to setup a mod than to make a whole casc 30GB+ file
it’s the old way of D2R modding… there’s a guy on YT that has D2R modding covered, in one of the videos he explained how to make small (mod only) modpacks and it doesn’t even have to be packed…
Oh, I am quite familiar with the -mod modname -txt method you speak of. The problem is that if you need to update the mod, you need access to the patched files, which you cant get without a functional tool to open and extract the data archive.
I also just realized that the comment I was replying to earlier, was from december last year, lol.
Yeah…
You’ve probably come to conclusion that ladik has updated the casc viever by now didn’t you?
;p
Considering I used the tool about a month ago… yeeah 
I don’t know where from You’ve donwnloaded this tool, hovever the version from 24 march seemes to work 4me…
You better watch the modding video once agin on how to operate the CascView…
also be sure you delete CascView from your game’s folder after you’ve extracted what’s nessecary, or Blizz might get the wrong idea you’re toying with their stuff for the purpose of online cheats and not for offline single player modding as it’s meant to be… You know better safe than sorry…
You are probably talking about a tuber by the name HighTechLowIQ, an yes, I know how to use Cascview.
If they flagged people for ban for that, then it would already too late for me. I even experimented with the mods, testing whether or not modded .txt files would function when the game is connected to Bnet, and they do with “offline” characters. I’ve still been playing vanilla online characters even with the mod enabled and Cascview + related files in the main folder of the game.
so how come CascView doesn’t work 4 You, but it does work for me?
Oh, I never said it didn’t work for me, just that its been about a month since I last used it. And my mistake replying to this:
Was I didn’t notice the date right away, thought CascView was broken in the recent patch.
sheesh… talk about musunderstandings… whew… I’m glad that’s over with…
anyways:
cool man…
SOOOOOOOO, it seems that the situation is just the same as last time I was here. Screw you guys, I’m going höööme, to quote Cartman of South Park. 
Not installing D2R again, it seems. I still want to enjoy a stable, slightly modded (equipment for followers) single player game. It seems that still is not possible, and to be Frank (which/who I am) I doubt it ever will.
Sayonara or sumthin’.
Nobody cares tho? Like you were SP, it doesn’t affect us, go away already.
What are you talking about? Of course its possible. I am modding game myself here:
I play with merc equip and made various other changes.
To @shnno1cares (btw, neither do I):
Ah, the warm embrace of fellow D2R players, heartwarming and touching to the last. We’re one big happy family here. 
And to @Zax a more diplomatic and proper answer:
If that is the case, I apologize, I have clearly misunderstood.
I assumed from what had happened in this thread since last I played D2R (very little, to be honest) that the reason I uninstalled the game back in Dec 21 still was relevant - that mods were being increasingly difficult to install and use (back in Dec 21 it was at the point where I quit completely impossible).
I am not looking for super-power mods and such, I am looking for mods that gives me the option of fully outfitting my hench(wo)man, and if possible also graphic mods that alter some of the less appealing character changes Blizzard made to D2R.
EDIT: I wrote first that it seemed that many mods on nexusmods were abandoned, but the merc equip mod at least seems to be up to date. I’ll take a deeper look into the mods at Nexusmods and see how recent their updates are, but I am all ears (and eyes) if there are other sites where I can find good mods for SP D2R.
Try here