So RAW, spells are weapons, And if it is a ranged spell, meets the requirements for sneak attack
No they are not, because of this text: "The Attack must use a
finesse or a ranged weapon."
Using a weapon at range to make a ranged attack is not the same as using a "ranged weapon": A ranged weapon is a specific type of weapon identified in the PHB. Ranged Weapons are: Light Crossbow, Dart, Shortbow, Sling, Blowgun, Hand Crossbow, Heavy Crossbow, Longbow and Net.
You can throw your longsword or hand axe at an enemy, that makes it a weapon used at range but not a "ranged weapon" and therefore not eligible for sneak attack.
A spell that is a weapon is neither a "finesse weapon" or a "ranged weapon" unless it specifically says so. For example, Shadow Blade says in the text of the spell that it has the "finesse" property, so that can be used for sneak attack because it is a "finesse weapon".
RAW the only cantrips I know of that is usable with sneak attack are Green Flame Blade and Booming Blade and only then if you use a weapon with the finesse property.
In terms of "Break the Game" a Rogue using a cantrip to sneak attack in tier 3 will put out substantially more damage than one that doesn't and this is true when using GFB or BB although that is limited to being used in melee within 5 feet and it is limited to one attack a turn. A Rogue using these can't use Two-Weapon Fighting, can't use extra attack if she is multiclassed and can't attack from beyond 5 feet. So she gets a substantial damage boost but with only 1 chance to hit and has to go into melee to do it. Further she can't use steady aim unless she is already within 5 feet and stays there.
For comparison if using Eldritch Blast with sneak attack a tier 3 Rogue will have 3 chances to land the sneak attack on his turn, eclipsing the TWF Rogue or even the multiclassed martial Rogue, with steady aim will be able to have advantage on one of the three attacks to boot and will do an extra 3 points of damage as compared to the current top tier which is using the cantrips noted above (with the limitations). That is quite a difference.