the bottom line is their crypto is not 100% secure if it can be accessed via seeds and private keys (even with billions of permutations)
The crypto is secure as long as they don't reveal their seed or private key to anyone.
Your
cash is not secure if someone has access to your cash. Your
crypto is not secure if someone has access to your crypto.
There are a LOT more than billions of permutations of a 24 word seed.
If you have 1 Billion planets in the universe such that on each planet you have 1 Billion people that each have 1 Billion computers and all those computers are all continuously try 1 Billion permutations per second for 1 Billion years, you still wouldn't have tried even One-Billionth of the possible permutations.
The same is true of private keys.
If you have 1 Billion planets in the universe such that on each planet you have 1 Billion people that each have 1 Billion computers and all those computers are all continuously try 1 Billion private keys per second for 1 Billion years, you still wouldn't have tried even One-Billionth of the possible keys.
Therefore, dictionary attacks on 24-word seeds and brute force of private keys aren't possible.
Furthermore, if you combine ALL the storage space that EVERYONE on earth has, there still isn't enough digital storage space on the earth to store a Rainbow Table of private keys or 24 word seeds.
Therefore, rainbow table isn't possible.
Keep your seed or private keys where others can't access them, and you will be fine.