We spent 35 years holidaying in a touring caravan (and are still doing in the UK) - initially in the UK and then about 20 years in Europe. We always shunned package holidays and loved the freedom of having our own accommodation and flexibility. Since retiring 15 years ago, we have been on 4 relatively short cruises and were surprised at how much we enjoyed them, so much so that we did our first World Cruise in 2020. It was FANTASTIC. Sadly COVID hit part way round the world meaning we could go nowhere but the ship. Everyone was "in the same boat" and the cameraderie had to be experienced to be believed. Fortunately there was no COVID on our ship, but we did get a substantial sum towards another cruise, so in 2023 we did our second World Cruise to catch all the places we had missed on the first one. Several others on the ship had been on the previous one, and as a result we made some now permanent friends. Next January, health permitting, we are doing our third (and possibly final) World Cruise with some different destinations.
It is true that you generally only get a day (or two) in each location (port charges are enormous), but the choice of shore trips is extensive and you can, of course, do your own thing.
We like a medium-sized ship - large enough to provide variety but small enough to meet the same people several times and make friends. Also the choice of on-board classes, shows, games, bars, speakers etc is more varied than with smaller ships. However we wouldn't want to go on one of the newer "giants" as you would find it difficult to make friends amongst so many.
We certainly spent money on-shore. Authentic meals, souvenirs, local arts and crafts etc. and enjoyed seeing something of the local life. In some of the poorer countries the arrival of a ship brought out local treats of music and dancing, including by local children in national costume, as well as famous landmarks, temples etc with experienced and knowledgeable guides. DH got his dream of attending opera at the Sydney Opera House (definitely without me!). I also got the chance to meet with a cousin who emigrated to Australia in 1972 - 48 years earlier! We also met his lovely Phillipino wife and their daughter, as well as the family of my late cousin in New Zealand, who had sadly died the year before.
It is not true that cruise ships are always a bad thing. All travel uses up resources, but there are strict maritime regulations regarding waste disposal and many ships handle it all on board. Some ports rely on the cruise industry for major parts of their economy.
Nor did we experience hoardes of cruisers clogging up towns, as shore trips were expertly organised and at staggered times.
Cruise cabins are not luxurious but of good standard. Occasional hiccups arise now and again (particularly with the plumbing!) but are dealt with quickly.
On the 2023 cruise there were few outbreaks of Covid among the cruisers who were immediately confined to their cabins and apparently well-treated.
We only wish we had discovered cruising earlier, though we probably would have no money left by now!