There is more, even if you don't play Dark Urge.
Main Plot of BGI+II is about Bhaal. Main Plot of BG3 is about the Bhaal, Bane, Myrkul trio with a heavy serving of Shar.
Three companions of BG I+III and one main antagonist are in BG3, two of them are companions again.
Many of the same monsters were used. Gnolls, Githyanki, even Doppelgangers in the city. Even when neglecting the brand mascots (Illithids, Beholders, Drow) and the generic ones like phase spiders.
Lots of books reference BGI and II and we have sidequest lines that are connected to sidequests from the old games.
It is not a particularly strong connection and certainly not continuing the same main story, but that main story was over.
AKA "In the Forgottten Realms Dungeons and Dragons Setting".
Bane, Bhaal, and Myrkul are the main villains (when deitys are involved) in something approximating 90% of the Forgotten Realms games Excepting the Drizzt ones where Lloth/Lotlth/Araushnee takees the helm. Or the period in 3rd ed when all 3 were killed off and effectively replaced by Cyric for a bit. Before gradually being returned because status quo lol (which also led them effectively all but retcon the entire plot of BG1/2/ToB itself out of existence (or maybe they'd didn't like Biowares interpretative licenses, who knows).
Nonetheless though, yeah. Tyranny, Murder and Death being consistent villains is pretty generic. But no ones ever accused the majority of videogames or D&D stories of being inspired lol. (funnily the last evil PCs I played in FR was a Ghaundaur following Drow who was paired up with an Urdlen cleric). Even though it turned out to be a devil impersonator, at least Icewind Dale had a creative twist for the evil priest that wasn't an obvious cliche.
The monsters are part and parcel of the setting (except Githyanki, who are typically associated with Planescape prior to its awkward graft onto Forgotten Realms when it was discontinued as its own settings). Githyanki for that matter didn't play any particularly notable involvement in the originals. With their only notable involve in a D&D game I can recall being Demon Stone (or the technically anomalous Githzerai Da'kon in Torment)
The return characters might as well be Easter Eggs, they either don't have any direct continuance with the original plots/arcs, or were even outright optional. (Also, another batch of retcons, as canonically every partymember other then the protagonist died, including Viconia and Jaheria (and Minsc, but he was specifically resurrected in some later story). It'd be like is Garrus Vakarian was in Mass Effect : Andromeda it would not functionally turn that into a direct follow on.
Some other thread there was a more indepth discussion about Series, but in summary:
Baldurs Gate (the title) doesn't anchor the series, as the entire 2nd/3rd (or 2.5) game take place elsewhere, before the 4th (BG3) comes back
It is a Forgotten Realms D&D game, but thats hardly a distinction. (you could also make a sizable argument that 2e and 5e FR are drasically disconnected)
The Bhaalspawn protagonist and main story line arc was concluded completely, turned into a non-ending and buried until they decided to retcon it for a single sentence to bring back Bhaal later. While there are Bhaalspawn (in the dark urge ending), it just comes off a half-assed lazy attempts to connect, as their is no logic as to why they exist given the whole reason for them is now moot and all previous ones were explicitly completely killed (twice even, thanks to that first retcon)
None of the companions were required for all entriesm and canonically they all died, so some of them shouldn't even exist in a direct continuation.
Like, unless the hanging point for the "series" is Sarevok (as limited as his presence in ToB and BG3 may be). This isn't a sequel besides a nostalgia bait name and some concessions. (and you can scroll back to read ad naseum about how its clearly a commissioned project for WotC's marketing, that Larian has injected ideas into at best)
Even more tenous would be to try and anchor it on Bhaal. Sure, Bhaal makes the Bhaal spawn and... is completely absent for the entire story. He could replaced with "an earthquake happened and sprinkled magic dust on these 20 orphans". The player can roleplay whatever they want, but every NPC Bhaalspawn doesn't appear to give a rats backside about the murdered-lord-of-murder. The memorable/notable villain, Irenicus, in the series has literally nothing to do with him and BG2 practically ignores the whole idea. (Hell, if you hired me to make a nostalgia grab off Baldurs Gate, I'd probably have Irenicus manage to come back from being dropped into the Blood War rather then try and upcycle Bhaal, cause hes the thing people actually remember lol. As ludicrously dumb as his backstory and motivation is)