Yes, I agree it's frustrating, but it's a similar situation for conjuration wizards as well.
Personally I agree with reskinning Find Familiar and Unseen Servant as kinds of undead creatures.
I also created the following spell to support early necromancers.
Animate Undead Beast
2nd-level necromancy
Casting Time: 1 minute
Range: 10 feet
Components: V, S, M (a bit and saddle)
Duration: Instantaneous
This spell creates an undead beast of burden. Choose a pile of bones or a corpse of a Large or Medium creature within range. Your spell imbues the target with a foul mimicry of life, rearranging its anatomy if necessary and raising it as an Undead Mount (statistics provided below).
The caster or a creature they designate can ride the Undead Mount as if it was a trained mount, or the Undead Mount can be used as a pack animal. If used as a pack animal, the caster can mentally command the Undead Mount to determine where it moves. If given a command, it will continue to follow that command until a new command is given.
The Undead Mount is under your control for 24 hours, after which it stops obeying any command you’ve given it. To maintain control of the Undead Mount for another 24 hours, you must cast this spell on the Undead Mount again before the current 24-hour period ends. This use of the spell reasserts your control over up to four Undead Mounts you have animated with this spell, rather than animating a new one.
At Higher Levels. When you cast this spell using a spell slot of 3rd level or higher, you animate or reassert control over two additional Undead Mounts for each slot level above 2nd. Each of the Undead Mount must come from a different corpse or pile of bones.
Undead Mount
Large or Medium Undead, Unaligned
Armor Class 10
Hit Points 19 (3d10 + 3)
Speed 50 ft.
STR | DEX | CON | INT | WIS | CHA |
16 (+3) | 10 (+0) | 12 (+1) | 2
(-4) | 11 (+0) | 7
(-2) |
Vulnerabilities radiant
Damage Immunities necrotic, poison
Condition Immunities exhaustion, poisoned
Senses Darkvision 60 ft., passive Perception 10
Languages Understands any language spoken by its creator
Beast of Burden. The Undead Mount is always considered to be a Large animal for the purpose of determining its carrying capacity.