They're not usually for the masses though is the difference. A flying ship may exist but no airports.
Clerics don't really get enough spell slots to heal en masse.
But yeah they can do things we can't probably not large scale.
A major city like Waterdeep features literally dozens of different faiths, and based on the spell casting costs (and the costs for basic items like food, weapons, trade goods etc) most low level healing spells (while expensive) would be within reach of the average middle class citizen.
A 'comfortable' Middle class lifestyle costs 2gp per day in basic living expenses (before you account for luxuries and goods), and a skilled hireling (anyone with a skill or tool) earns a
minimum of 2gp per day.
From that we can extrapolate a salary of around 100gp per month (around 3 GP per day) for a middle class person.
In Tyranny of Dragons, the following spellcasting services are available:
- Cure wounds (1st level) 10 gp
- Identify 20 gp
- Lesser restoration 40 gp
- Prayer of healing (2nd level) 40 gp
- Remove curse 90 gp
- Speak with dead 90 gp
- Divination 210 gp
- Greater restoration 450 gp
- Raise dead 1,250 gp
Effectively spellcasting seems to cost roughly ([level x level] x 10) + costly material components.
Raise dead is effectively a years salary, and you can speak with a dead relative or the victim of a crime for one for a months salary. Gaining information on a rival business or loved one, or the person who murdered your Aunt Mildred via Divination costs 2 months salary.
For the truly wealthy (or those in the good graces of a particular faith) you can have a limb regenerated, be cured of cancer or other diseases, be brought back from the dead months after dying, be cured of blindness or deafness etc.
All far more advanced than our current medical technology allows, and beyond even Star Trek levels of medical technology.