For all re Cruises, first differentiate between the round Britain ones, and others to say Baltic or sunnier climes. Cruise regulars will know a lot of the key points, but not 'newbies'.
Tendering is NOT to everyone's taste, and it can severely slow up your day. The bigger ships invariably have to use that method in smaller ports.
THE biggest criticism on cruise blogs and forums is certainly SHIP's TOURS! Yes, easier to select one or two, get on the bus, etc, but they get castigated for being poorer value than doing your own thing, and you may get stuck with being talked at by a well-meaning guide for hours on end?! [IF you're somewhere like Greece, funny alphabet, you may have little choice as using public transport may be tricky?!].
Saga is popular with the older generation, lots included, but NOT cheap! Fred Olsen is a line that is geared to the more mature British customer -- and they usually have smaller ships. Azamara is an excellent 5 to 6 star line, smaller ships, great service at not quite the eye-watering prices of say Oceania, Seabourn and the like.
Most of that class of lines are 'smart casual', so if you don't like the formal dining thing on some nights, you don't have to. HOWEVER, almost every ship (any type, the elite, or Olsen, Royal Carib, Celebrity, Princess, P&O etc) has a 'buffet' restaurant, for evening meals beside b'fast and lunch, and they do NOT REQUIRE dressing up! And, what may be a plus for some (?), in the buffet you will have the option of selecting from most of the Main dining room choices - but it's not compulsory! - or even, if you like, you can select say 3 starters and 4 puds, mix and match as you like.
Lots of cruise websites to help choice, Cruise co uk has masses of info, IGLU Cruise is a terrific agent but plenty more.