Cantrips can be cast again freely. Casting a cantrip is a caster's version of swinging an axe. They both cost no resources and have the same chances of hitting, assuming equal stats.
Edit: For levelled spells, I agree with you. The combination of more difficult encounters (encouraging either cheese or spending lots of spells), the ease of long resting (~free), and the relative reduction of utility spells' worth due to easy advantage+other abilities/consumables, and the ease of losing concentration due to surfaces all harm combat enjoyability. E.g., in 5e I would spend a spell slot to use Bless and be happy with my turn, but in BG3 it's just so much better to spam attacks.
I checked, it's two actions, one for rank one, one for one rank two spell, neither can be cast again until rest, neither can be cast in combat rendering them largely useless because you could just go to camp and sleep outside of combat.
I do admit that after playing the game with TT going through the Prologue, it is still incredibly hard using 5e rules. If you read my post about BG3 as Tabletop, you'll see that the player, Diadell, almost loses every battle. Did she survive? Yes. She made it through the encounters, but fighting Imps at Level 1 even with Lae'zel and We are Here, is not easy. It is hard.
It gets ridiculous later on. Once you take out the Goblin bosses, two of which have half a dozen support characters in them, one of which has two but also a patroller minor boss who turns up at the worst time, but outside in the Goblin camp there are thirteen - 13! - Gobilns and something bears (sorry, can't remember their name), two of which are spellcasters with one-shot-prone spells, one Worg (minus the summons), and a Troll you have to fight.
If you consider that bad enough then try it with a spell caster who can only access a single rank 2 spell, falls asleep whenever sleep spells hit him, and can only use his ranked spells once in battle, along with melee characters that miss more than they hit. To make matters worse, it's impossible to sneak back in through the main entrance because a Goblin has line of sight covering the path you need to cross to get to the door, and despite searching all over, I couldn't find an alternative.
The encounter is not survivable with the available armour, the only way to do it is an extroinarily long, attractional battle on the bridge, or call in Troll support but given they cost 500 gold a battle, you won't be able to afford them for the three battles you ideally need them for. If your character had better gear, and the game had a viable spell casting system, and you hit more than you missed, you'd still struggle against those odds, and the game has none of that currently.
There is indication in Datamining that we should eventually be able to free SH and have her join us for the ship battles, and in general I think the game if moved toward 5e would be more genuinely balanced with a 6 person squad as that would remove that out numbering issue and so encounters would be more fair (and their difficulty will be more tailored to the player)
I'm not sure a six member party will work all that well in the game, the screen would start to be cluttered and it would increase the minimum specs for running the game, therefore reducing Larian's potential customer base and their profits along with it. What they need to do is balance encounters by making it easier to bypass them or give the player terrain advantages they can use such as choke points, reduce the miss hit rate for attacks, and rework their entire magic system which currently is not fit for purpose. Here's an example of how unbalanced it is. You know the encounter you have at the beginning of the game? The one with the Halfling and his Elf sidekick in the temple ruins? There's also a mage there if you chose to fight. She can put any of your characters to sleep but is immune to sleep herself. That is egregiously unbalanced and should never had made it into the game.
