I hate the gimmicky "EK cantrips" (Booming Blade and Green Flame Blade) that were some kind of an attempt to make War Magic decent. Those cantrips didn't fix the class, but trapped it into using those exact Cantrips and nothing else. EK needs to be flexible like a 5th level EK attacking once, and then throwing a Fire Bolt at another distant enemy. That gives them something unique.
Those cantrips aren't that good for Eldritch Knights anyway; they're best on classes that only get one attack, or have a maximum of two attack with no action surge.
Ultimately Eldritch Knight in Baldur's Gate 3 is a lot like Eldritch Knight in 5th edition D&D, exactly as they aimed for it to be; it's a Fighter with a little bit of spellcasting sprinkled on top. You don't want to use action spells because that means you're not doing what Fighter is best at, namely making a bunch of attacks; you want spells you can do
in addition to that, and which don't care too much about your Intelligence. That's why Shield is so good, likewise Magic Missile, some other highlights for combat are Expeditious Retreat (ironically for running
towards enemies) and Fog Cloud. For cantrips it's all about the utility options like Friends for advantage on charisma checks, Dancing Lights or Light to cope with darkness, Mage Hand for fondling distant objects, and maybe Minor Illusion for triggering traps (since distracting enemies still uses the DC).
That said, it's not impossible to build an Eldritch Knight, but you'll be building them very differently; e.g- you'll probably want to focus on Dexterity so you can be more of a ranged character, that way you don't have to worry as much as Constitution (you'll be trying to avoid taking damage by being distant), this then frees you up to take more Intelligence so you can use attack and save DC spells. But that really requires you to plan for this from the start (start out as an archer, then become more of an eldritch archer later) or you'll likely need to respec later.
