Originally Posted by
Person_Man
Put another way, what benefit does the Eldritch Knight Fighter 20 get that a Fighter 2/Full Caster 18 doesn't get?
Extra Attacks? Sorry, but just using a Cantrip and/or spell or spell buffed attacks scales just as well or better for most other classes. And unfortunately the Eldritch Knight can only make 1 attack + Cantrip per round, or 2+ attacks, but never both. A second Action Surge at 17th level is indeed useful. But it can only be used once per Short Rest, and is not as useful as a Sorcerer's Metamagic (which is essentially a spell only Action Surge that can be used multiple times per day) or various Conjured creatures (which multiply your action economy).
Unfortunately, I think that the Fighter just falls behind starting at level 6ish+, and none of its subclasses options can fix it.