It was never impossible to make ASICs for coins, but it has to be a good business to build them buy them.

There are 2 directions nowadays:
1. ASIC resistant coins that after some point get mined by ASICs or become worthless. It still takes long until ASICs are designed for them..
2. Coins that change algo from time to time to make it become bad business to invest in ASICs.

The current state of POW
Proof of Work (POW) requires a service user to demonstrate that they have made a donation (usually the cost of performing the operation) to prevent network attacks such as spam and Dedicated Dedicated Service (DDoS).
In relation to Bitcoin, PoW means evidence of bitcoin digger's contribution to virtual money exploitation.
Peer-awarded peers are often rewarded with newly created currencies and transaction fees.
The influence of peers on network consensus and their reward is determined by the volume of transactions they deal with.
In other words, PoW is asking to create a block on the blockchain distribution accounting book.
Mining plays the role of:
- To verify the legality of a transaction.
- To create new digital currency by rewarding diggers.
When you want to set up a transaction:
- Transactions are packaged together into one block.
- Miners verify that transactions in each block are legal.
- To do so, the miner needs to solve a math puzzle called the PoW problem.
- A reward will be given to the first miner solving each block problem.