It is because until recently it was thought that there was basically no value to these things after the game had been out for a few years. If a game was popular enough you got to reuse the assets to make expansions and sequels, but after a few years if you hadn't done that then the game was abandoned and the assets were useless. No one thought that there would be huge nostalgia for these games or that people would want to remake them 15 years later.
Also remember that it was a different time and a very different industry. It was not the corporate machines that the likes of EA is today. The original Baldur's Gate was made by a group of people that had never made a video game before, run by two doctors doing it as a side project. They were literally figuring out as they went along.
So from what I can tell, patch 2.0 is NOT being well-received by the D&D diehards. They're not liking the new UI, the patch itself is very buggy, had some unintended (?) consequences of wiping out save files etc.
Several people on the Beamdog forums who (at least) sound knowledgeable say that like previous patches, Beamdog will likely hotfix and clean up some of this mess in a few weeks.
I bought BG:EE and BG2:EE during this current GOG sale. $5.98 for the both because I had the original versions. But I think I'm going to wait until the dust settles before loading them up and attempting a play through. Maybe this summer.
I haven't played much of the new version, maybe couple hours.
I didn't have a previous save that I cared about. I really like many of the new UI changes but it is one of those games that people just don't want it changed. It is almost weird.
Honestly not sure what I think about the new character graphics. Little more colorful, you can zoom in and out which is super handy, especially for fonts. But at the same time things look a bit fuzzy and just ...odd.
It doesn't make this a rush out and buy, but personally I am leaning towards liking things being freshened up.
As for bugs with the ruleset and mechanics, I have no idea if that exists...I haven't played enough to notice. I think I heard that the cleric/Ranger bug/exploit ( access to all druid spells ) was finally fixed. But you can undo that easily with a baldur.ini change.
Upon starting the game, it looks like many of the menus have changed, many of the interface options and buttons totally moved or reworked, and most noticeably, the actual character sprites have been completely redone to be almost brighter, more like a mobile game. I'm not sure how I feel about it honestly, luckily I don't get too hung up on visuals anymore.
I just bought the steam version of BG1, and glad I am not the only one who noticed something terribly wrong with the graphics. They basically just messed everything up, the original graphics were just fine.