Yeah the Green Dragon fight in Solasta is way harder than any unmodded BG2 dragon fight. I can get having rose colored glasses -- Firkrag was really tough for me the first time I fought him at age 14. But he is pretty easy to shut down in a few rounds. The Solasta dragon is pretty hard to shut down because of its incredible movement speed, its legendary actions, and its legendary saves. You have to have some meta foreknowledge to counteract some of the aspects of the encounter, particularly the MMO style puzzle with the lightning pulses.
It's not like BG2 is a lost artifact that you can't check, either. Load it up and fight Kangaxx with your current meta knowledge. Nigga dies in three seconds and none of his abilities do anything if you cast a few important buffs ahead of time.
The criticism of Solasta that it veers between trivial encounters and tough, tricky ones is an accurate one. There are only some areas in which there is any attrition-centric encounter design, like the second lava forest in which the placed rest fire is at the end of the zone and is otherwise inaccessible. To rest scum that area you would have to retreat off the map, rest, and come back. In a lot of other areas they plop out a long rest zone in a central location or after every major encounter.
IMO allowing rest any time is fine in certain campaign circumstances, like when the party is exploring. It gives the players the opportunity to explore their characters, try things out, and get more resources. The issue of not having more pressure time periods is one of campaign/quest design. There are tons of scenarios in which time pressure or resource pressure make sense and are natural to the fiction of said scenario. This is also an issue in which some scenarios are only interesting if you do not hand wave away logistical mechanics. Planning an expedition into the desert to raid tombs is easy if you have hand-waived away the rules about water or the material components of spells that allow you to create it. If there is no such thing as hiring workers to drive wagons into the wilderness that you will have to defend from monsters, then your 'expedition' is just moving your party of tokens who do not eat or drink 200 miles to get some 'loot' to give you math bonuses in combat resolution. All of these management sim type gameplay elements are more interesting RPG challenges than """story""" stuff that always ends up being disappointing. These types of human issues also underly many superb stories in literature, but they tend to be ignored by game developers as being 'boring.'
Solasta's travel system is more interesting than a lot of other similar games, but it's overly abstracted and too easy to overcome. Once you get 'Create Food," it's all over as something that requires a little planning in advance. I would have happily traded all the dialogue in the entire game (except for the line about orcs being like "dwarves, but worse") for a better random encounter system and more in depth adventure mechanics. Dialogue and story are plagues on the genre. If just half of storyfags learned what a 'book' was, developers would no longer feel the need to cater to their stupid and unfulfillable wishes.