As per my understanding, if the Mempool TX fee is high, this means that miners are making more money and this suits them right ?
Yes, although the difference is generally not huge and the block subsidy still makes up the majority of their rewards. If you look at a recent block, for example, you'll see the mining pool earned 6.25 BTC from the block rewards and only 0.12 BTC from fees. Even if you look back a week or so to when minimum fees for the next block were 50 sats/vbyte or more, then the miner is still only earning 0.5 BTC from fees, so less than 10% of their overall block reward.So this Bitcoin Ordinals thing, which is not liked by many of us because it makes the bitcoin blockchain congested, the miners would like it because it then helps them get more fee for mining?
Yes.Also, this means that when the mempool fee is low, the miner's reward becomes low too, again a situation not favourable for miners 
It becomes lower, but not too low. As time goes on, thn miners are using more and more efficient hardware and source cheaper or even free electricity from renewable sources, allowing them to continue to make profits and operate despite their rewards falling. Indeed, global hashrate is currently at an all time high, around 410 EH/s. 
