Groundbased
You are correct that it is a 737-300 of some 24 years vintage, not that that in itself is a problem to me. It is not what I expected/paid for when I booked.
So when you've paid Monarch, you've obviously expected to get a Monarch's own 25 years old 757 or 23 years old A300 or 20 year old A320 instead of "old" 24 years old Lithuanian 737? Get a live man!