Not a full answer, but the best reaction depends largely on the metagame of what you're playing. If you have a big Water-type weakness but there aren't many prominent Water types moves used in the format, it might not be a huge deal. On the other hand, you'd deal with a known popular threat like Gyarados differently than one like Toxapex. So yes, you need to look at which POKÉMON are used more than others, not just which types, because not every weakness is created equal and because Pokémon can learn moves that are different from their own types. For instance, tons of non-Ground Pokémon carry Earthquake/Earth Power and non-Ice Pokémon carry Ice moves specifically because they are excellent coverage moves, so you can't just think like "My team is full of Dragons that resist Water, so I don't need to worry about Water-types." Abilities matter here too. And not every Pokémon on your team is going to be indivifually well equipped to deal with every single situation–they're on a team so they can help each other out.
