After playing 16+ hours I would like to update the feedback with general things.
The game plot is based on the DOS 2 or at least feels the same, but it’s not That issue for me.
The main concern is the fact of missing the core idea of the TTRPG in general and D&D in specific.
Although, the idea of “bug-in-the-head-that-is-so-special-and-that-is-only-reason-why-everything-is-happening” is gross. There is a ton of ways, how to solve the problem, but always we are failing, cuz it’s “special”! D&D is not dealing with exceptions, but with rules.
The idea is to provide the player with a world that is living by straight rules, a goblin is always a little goblin with a DIY spear, and a knight is always geared monster slayer. So, the goblins very unlikely to have any special equipment or 100+ g.p. loot. This point is essential to make the world clear to the player and to make it feel Real. Or scrolls may be used only by casters, or that the True Resurrection is the mightiest healing spell, that may solve ANY problem, or then Ilithids have to use Mind Blank (8th LVL. spell) to be free from BigBrains Co., but not the little cheap Ring of Mind Protection. Yes, this seems to be meaningless, but it is the core of D&D to make it work and real.
Next essential point, is that Skills are made to help the player to solve problems, not to Forced them to get any suitable outcome, not to punish them. The Skill check is supposed to be resolving for the whole situation, that means, that if you scared the gith, he will be feared of you for all the time and the situation will be resolved based on that, no further checks needed.
The fights. The fight in TTRPG is a clash of opinions, the fight for some purpose with feelings on both sides, plot and interaction. The attack rolls spells and so on just giving the bones for it. The “-100 hp” is not the aim, but only consequence of that, for instance, that after receiving such a damage goblin will dramatically explode in the air, and the dragon may be scared and deeply wounded by such a terrifying strike. That is what essential, to show reactions, emotions, wound and how it affected them, so the goblin, left in 1 hp is most likely to surrender or will cry for help and try to disengage and so on.
Summing up everything. D&D is a strongly ruled system with the straight approach toward any event, that may be reproduced with the same result. This ruleset helps to make a good story, giving the DM a ground for all that is happening on the “stage”. The dice rolls are not meant to be punishing but only helps the players to advance the story in most likely interesting for THEM path. The story is closely bounded with ruleset as it gives bones to it and makes world “real”, as the players gain the experience of “how it is working in the world” and may easily understand the power on the NPC caster by the very minor things, like to be scared, if they see, that he is capable of permanent polymorph as the has a “frog-prince” on the shoulder. And I hope, that game designers understand examples given.