Reliable can also be determined either by the frequency of failure or problems once failures occur.
Perhaps a Rohloff IGH may fail less often but if it does, you will have a long wait until it gets serviced and returned. No local shop will do that for you.
A derailer may fail more often (I've never had one fail on tour but everyone's example will only be antedotal) but it can repaired or replaced at most local bike shops.
Same logic applies to belt drive. Walk into a shop and see how many replacement parts they have in stock.
Revelate is a popular brand because they are light bags and were a good choice for racing bikepackers. They got a lot of good press off of that. Popularity does not equal reliable. Probably, from a practical perspective, Ortlieb seems to be a reliable bag of choice for bike tourists.
Brakes. Mechanical is probably easier to service in the field but hydraulic stop with better modulation. Reliable in different ways.
Tires. The most reliable would be solid rubber but the ride would suck. The spectrum between puncture resistance and speed goes on from there. Tubeless vs tubed depends on conditions I think. Ultimately if a tubeless tire cannot be repaired you throw a tube in it so... I run tubes with Stans fluid in them as a compromise. Some will or won't agree.
Everyone will have their own opinions for this question. There is no right or wrong, just perspectives. Look to the reasoning rather than the choice.