We have done 5 Caribbean cruises with MSC on Melody/Lirica/Opera and loved every single one. For us they are now No.1 choice.
Lirica is a beautiful ship. Simple and elegant decorative schemes and all understated. Gimmick free. You will enjoy each day without continual announcements and hassle/sales pitches/exhortations to buy this or that.
The suites are very nice but generally the cabins are compact and the showers are small and with "sticky" curtains.
The food which is very good has a European style (Italian for Italians) and feautures some wonderful seafood, pasta and risottos each day.
Service has always been first class. However you will need to request service - with a smile, a word, a raised finger because no-one is going to chase you to buy a drink or anything else.
Once there were always Italian wait staff in the Caribbean. Mainly they were experienced waiters from Restaurants/Hotels in Italy who were working a cruise line during the European winter months. As MSC has expanded they have had to employ from elsewhere. This means quite a few East European wait staff but also Balinesian etc.
The animation teams are brilliant fun people who will liven up every moment of the day and night if that is what you want.
However if you want a simple more sophisticated style it is there for the taking with excellent musical artistes performing in the various lounges at night. These people range from latin to pop to jazz to classical.
Shows are vey much "visual" and in a purpose built theatre. No smoking and No drinking allowed There are good comic acts, good singers, musicians, dancers, magicians, acrobats/trapeze etc. What drives some folk mad is that in the theatre introductions are always in English/Italian/French/German/Spanish. Although in the Caribbean season there are a large number of American/Canadian passengers you will certainly be joined by people for whom those languages are mother tongue.
You will read some terrible things about MSC but it seems inevitiably to come down to attitude.
People who are travel wise and experienced and can accept something different (in fact this is what they seek) seem to love everything about the line and the ships.
Others have fixed ideas and want everything to be just like it is at home,
different is not different, different is wrong and these folk hate it.