It's DF... You roll the dice and hope you get someone who has a similar playstyle and mind set. Don't get upset when they aren't what you are looking for. It's a party suggestion to ease getting 4 (or 8+) players together to attempt content. It doesn't always work out and there will be varying levels of competence with each player. /shrug

If you want more control over expectations, you'll need to expend effort getting a group together outside of DF.