I did some additional digging. Magic Items and Critical Hits (Dungeon Masters Guide Pg. 222)
Magic Weapons and Critical Hits: Some weapon qualities and some specific weapons have an extra effect on a critical hit. A flaming burst weapon, for example, does extra fire damage on a critical hit. This special effect functions against creatures not subject to ...
It's not supposed to work because you can't SCORE a critical hit
Rolling a ''critical'' (threat) is not the same as a critical ''hit'', creatures immune to critical means you would normally do a critical against such a creature (example: a human vampire) but you don't.
Furthermore a part of what you shared makes it clear to me:
When you score a ...
Once a day with a 67.94% chance, sustainably once per turn with a 38.59% chance.
Race: Elf (Any) or Half-elf (Any)
Feats: Elven Accuracy (XGE), Lucky (PHB)
Spells: Find Familiar (PHB)
Magic Items: Luck Blade (DMG)
Champion Fighter 15
Divination Wizard 2
From Champion Fighter, you succeed at scoring a critical hit on 3 out of 20 dice ...
Not as bad as you think.
You're overestimating its power. By default, a point of crit chance is actually a little bit less valuable than a point of to-hit. +1 to-hit means that 1/20th of the time, you have a moment where you would have missed (doing no damage) and instead hit, doing full damage, plus any secondary effects that may apply. +1 to crit means ...
They are vehicles, but whether or not it is an object may be up to a DM
The stat blocks for them list them as vehicles so that we know. But whether or not a vehicle is an object has been debatable on this site for awhile.
The DMG describes objects as :
For the purpose of these rules, an object is a discrete, inanimate item like a window, door, sword, ...
Using just the Player's Handbook and Dungeon Master's Guide: just over 81%
A Champion Fighter 16/Diviner Wizard 2 with the Lucky feat and a Luck Blade.
First, your Familiar will Help to give advantage, then use your action to make your attack. A combination of Superior Critical, Halfling Luck, Lucky and your Luck Blade give you about a 49% chance of a ...