A couple of things, I think that the lore on creation of undead is not as understood as suggested in the previous post. A prime example is
https://forgottenrealms.fandom.com/wiki/Baelnorn_lich Which are elven undead defenders that can be created by elven high magic via the school of necromancy and are not "summoned" through divine means.
As for the evil descriptor, descriptors only purpose in 3.5 is for cleric restrictions. This is for divine based casting as certain spells are not within the domain of certain deities, The evil and good descriptors exist for simplicity as undeath isn't a descriptor.
On alignments and the shifting of alignment based purely on casting a spell, the rules in 3.5 don't address this and would be server specific. The only thing that a DM may consider the adjustment of alignment of one of his players (in PnP) is through character intent.
Elven High Magic is spells and magic that exist outside of Mystra's ban and her direct governance. In fact, every High Magic spell has to be sanctioned by Corellon Larethian himself

High Magic is entirely governed by the chief elven deity of their pantheon and that alone makes it governed by divine means. It's also not just any magic that anyone can access and/or master. If you read more about Baelnorns, you'll also learn that their existence and creation is very carefully observed by Sehanine Moonbow- yet another elven deity. It's not a process that involves 100% mortals at all.
Descriptors aren't only mechanical- they literally define the nature of the spell. If something has an evil, good, chaotic, fire, water, lawful descriptor, then the spell is of that cosmical type and it invokes that
factual cosmical power. A spellcaster using such spells is literally channeling those cosmical powers around him and through himself. Those spells and their effects regarding alignments or elemental heritage -matter- in a literal sense. Maw of Chaos, abjuration spell, is a chaotic spell and it will leave Chaotic characters mostly unscratched, while non-chaotic ones are in for a very bad day.
As for the alignments...
3.0/3.5 does speak upon it

The reason why it's stated here that they "may get away with it" is that it's still an evil spell and it still leads you towards becoming evil, but if you're doing it for arguably good actions- you may not become evil or at least not as much as you could've
(To put it in example, let's assume casting an X spell nets you 2 evil points, but you're doing it in order to save a group of innocent refugees from a merciless warlord for no payment at all, which nets you 2 good aligned points. It means you come out at 0 points either way). If you're using spells that are channeling energies or will of cosmical evil/deities that are a representation literal evil, don't be surprised if that power changes you towards being evil.
Going back to undead topic, though, there of course exist non-evil undead. Crypt Things, Baelnorns (as they are loved to be brought up), Revenants, Shadowdancer's Summon Shadow, Archliches and etc. However, what people seem to forget and what DM Golem have stated, those nearly always have a divine background at them or otherwise specialsauce supernatural background (Undead create themselves, or Shadowdancer's Shadow).
By no means it's any type of conventional magic, at all. Conventional magic is simply unable to create non-evil undead without having a divine means to back it up, and then it's non-conventional anymore
(Tyr directly making Militades, Hoar giving his priests the power of creating Revenants in 2nd edition (though he's Neutral, not good aligned), Corellon & Sehanine overseeing and sanctioning creation ONLY of Baelnorns, even Archliches have a divine spark behind them, because they get Turn Undead ability which is not a standard undead ability whatsoever).