my understanding is that within Forgotten Realms lore, Deities are still a very large part of a Paladin's Oath of Devotion.
Your understanding is a little faulty here - not entirely incorrect, but a little off the mark.
Deities can be a large part, sometimes, and for many Paladins they are across all the realms, but they're not a necessary part by any means. You do not need to be dedicated to a deity, and it is not a pre-requisite in
ANY realmspace, FR or otherwise. I'm not sure where you've gained the idea that Oath of Devotion specifically, in the FR specifically has intrinsically anything more or less to do with deities than anything else - it doesn't.
Following a deity is
one option. It's an option
many paladins follow - Many; not "all", not even "most", just "many".
We absolutely should not, under any circumstances whatsoever be
required to select a deity for our paladins.
We
should absolutely and with my complete and full support, have the
option of doing so, because it is a valid option that many paladins take, and those who wish to follow a deity should not be denied the acknowledgement of doing so. Just so, those who don't should not be forced to. You don't need a deity to properly codify your oath's tenets - you just need to properly codify the tenets; a divine intermediary is a redundant and optional step in that process that one can follow if they are called to the duty by a deity they already follow, or if they choose to follow one that matches their duty.
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Better notifications of what will count as transgressing the tenets of your oath is definitely necessary and a good point to make, so a definite +1 to that element.
Frankly, I'd rather it not try to tangle with oaths and breaking them at all, than to emulate the kind of destructive, antagonistic, sweaty DM behaviour it's designed around at the moment.