Well, if I use your argumentation, then side quests are also non-sensical.
The shitty ones where you have to kill the rats in someone's cellar or bring someone 20 wolf asses for no actual reward but some XP? Tasks no sane adventurer would actually bother with in universe? Absolutely.
Optional quests that do provide tangible rewards, however, could be in.
There are some exceptions to the former:
-auxiliary quests, where you can accomplish some shitty and unrewarding quest at no additional effort while doing something more important - deliver a letter/package, while going to another city for some other reason; find someone's stolen family heirloom ring while purging an MQ dungeon of bandits.
-quests that may not be rewarding or obligatory, but can be considered important matter (help, bandits murdered my family, but I'm too poor to give you anything for your risk and effort). They still should rather not reward you unconditionally, meaning overall cost (whatever it might be) should exceed absolute total value of whatever rewards player can expect, because otherwise everyone qualified would become a non-profit scourge of the wicked. Game should allow you to do the right stuff even at net loss, but to make it actually matter, the net loss should stay net loss.
-low level guild quests where you're forced to do menial work in exchange for opportunities to rise in status.
-chores you perform exclusively for monetary rewards if the economy isn't completely broken somehow.
-if your quest system involves some representation of opportunity cost for every quest you can very well have a lot of unrewarding shitty filler for the sole purpose of kicking hopeless completionists and people too dumb to discern worthwhile quests in the arse.
Still, the quests with sole purpose of wasting my fucking time should not be included just like encounters and systems with sole purpose of wasting my fucking time should not be included.
Kill xp also does not mean that you will kill everything, just like you will not kill everything for loot. You have the choice to do so and will only do it if you want to or need to.
The choice between reward and lack of reward, with no strings attached, is not a choice.
If I make a druid in BG and optimal way to play this druid includes going out of my way to find and slaughter bears and other wildlife for XP and XP alone, then something is fucking wrong with this game.
Which isn't choice.
to just making combat redundant is not a good idea in combat based game in my opinion.
How thoughtful of you to have italicized the main fallacy yourself.
RPGs are not inherently combat based games.
RPGs are not ideally combat based games.
If you're making an RPG and treating it as combat focused game you're essentially making a H&S/FPS/crawler/tactical game, except inferior, because you keep blowing your funds on shit completely unrelated to central mechanics.
In other words - you're doing it wrong.
The core part of a proper RPG is that it concentrates on what given player character can and cannot do, as opposed by all the other player characters in the same game, and gives player options to decide what they want to attempt. This means that no individual conflict resolution subsystem should be the focus of an RPG but rather their interplay, filtered by the capabilities of player character/party and player's choice.
This also means that going for combat XP or any other activity-based XP in an XP based system is plain fucking wrong, because it shifts the focus of the game to something which it wasn't build around of and relegates other conflict resolution mechanics to the rank of monument to resources wasted during development.
Removing combat XP doesn't rob combat players of anything. If you complete the quest using combat, quest XP is your combat XP. If you complete it using diplomacy, quest XP is your diplomacy XP. If you complete it
via stealth, quest XP is your stealth XP. If you complete it by cleverly employing emergent mechanics
via crazy, but entirely logical in hindsight use of rope, barrel of pitch and two midgets, that wasn't actually foreseen by the devs but nevertheless isn't a bug or exploit then quest XP is your creativity XP.
Why should combat characters get additional XP for adequate use of their favoured mechanics, but not the others?
Finally, it doesn't make combat "redundant". If your character can't do anything but fight, then you won't have any other choice. If your character is and excellent sneak, but couldn't fight his way out of wet paper bag, then combat will be a non-option for them, because it will only get them killed. Various solutions may give varying material or systemic rewards in various quests, for example there might be quests where sneaking make you miss out on some potential rewards, but there might be ones where it's combat that works the worst. Typically there should be more than one solution realistic for given character, but not all kinds of solutions should be always available, so overspecialization would be penalized and just going through game mindlessly repeating *sneaksneaksneak* or *fightfightfight* when confronted with an obstacle should get you nowhere (actually somewhere, with this somewhere being an early grave).
Oh, and not only should there be no action XP in an XP based system, but the XP gains should not be results of every quest. Only quests or mutually exclusive sets of quests that every player character should be realistically interested in doing should result in XP rewards. This means that game's critical path can give XP rewards, mutually exclusive quests of which at least one should be desirable by any character can give XP rewards and neutral quests can do too, but not quests like "set orphanage on fire for teh evulz" or "give at least 10 mercy blowjobs to the lepers while saving kittens".