Why they said that their changes to D&D are needed for the video game environment when Solasta proves that this is not the case.
Come now, we know why.
'Will there be a map designer?'
That would be my question.
Ok i am curious... Why??
They didn't try from scratch. This is a mod of their own games.
This is correct, except that it is an engine revision rather than a mod. The reason that Larian and WotC came to an agreement is probably that they both felt that the Larian DOS/DOS2 engine fit the requirements for a coop DnD experience.
Obviously Larian already have capabilities in the Engine from DOS2, which they mapped onto DnD where possible, before revising the engine to add features not already available. I'm sure Larian regard their core audience to be the people that bought DOS2, so it is important to keep that audience happy, while trying to expand the audience to new players attracted by Baldur's Gate and DnD material. Keeping everyone happy would only be possible through a fairly Byzantine set of optional behaviours.
Solasta, by contrast, is starting from no particular expectation, and aiming to build an audience mainly from the TableTop D&D player base. So they implement the current rules quite closely, and ( I assume ) accept that the wider videogame audience will probably find the game rather slow and uninteresting.
You can do ( almost ) anything you want when developing a computer-base game; the problem is finding something you want to do that is also commercially viable.