How to open a conversation that goes somewhere
'Hey' is not a bad opener because it is lazy. It is a bad opener because it gives the other person nothing to answer, and the whole job of an opener is to make replying easy.
What a good opener actually does
Every message that gets a reply does the same thing: it proves you read something specific about this person, and it leaves an easy way in. That is the entire mechanism. It has nothing to do with being witty.
Compare 'hey' with 'you said you cook badly and hike well - which one is the lie?' The second one is not clever, it is just answerable. It refers to something they wrote, and it invites a specific response rather than a general one.
Comment on what they wrote, not what they look like
A compliment on a photo asks the other person to accept a compliment, which is a small social task. A question about something they wrote asks them to talk about themselves, which is a pleasure. One of these gets replies and one does not.
This is also why prompts and answers are worth filling in on your own profile. They exist so that somebody has something specific to open with, and profiles without them get fewer messages.
Ask something with a real answer
Closed questions end conversations. 'Do you like travelling?' gets yes. 'Where is the best place you have been, and would you go back?' gets a paragraph. Aim for questions that cannot be answered in one word.
Match their energy rather than their word count
Short replies are information. If somebody consistently answers in three words across several messages, they are either not interested or not in a position to date right now. Neither is a reason to keep writing longer messages hoping to compensate - that is how a conversation becomes a monologue.
Give it two or three exchanges. If it stays one-sided, stop. There is no version of this where persistence works.
Move towards meeting, deliberately
Messaging indefinitely is the most common way a promising match dies. Once there is a bit of rapport, say plainly that you have enjoyed it and suggest something small and specific - a coffee on Saturday afternoon, a walk on Thursday evening. Specific beats open-ended, because it is easy to say yes to and easy to suggest an alternative to.
If they avoid it twice without offering an alternative, that is an answer. Take it, and move on.
The things not to do
Do not open with a complaint about dating apps. Do not send a message that could have been copied and pasted to anyone. Do not ask for photos, contact details or a move off the platform before there is any reason to. And do not treat a slow reply as an invitation to send more.