So I am wondering how come eth network got congested when block size is resizable and it can take more trx if needed? I am reading some info that it can do that but miners don't want to do it as it causes them to basically earn less. Also I see in this post Why don't Ethereum increase the block gas limit? that miners can even mine empty block to get advantage, how come this is possible and not banned in consensus mechanism?
Most of the miner usually want to maximize their rewards. The whole consensus protocol is based on that assumption.
If a miner mines an empty block he gains the block reward. But he doesn't get the gas fees from transactions. Therefore he is incentivized to include as many transactions in his block as possible to get the biggest reward - including and executing the transactions doesn't cost almost anything for the miner compared to the effort of solving the Proof of Work "puzzle".
As for why not increase block size a good answer is already provided in your link.