I understand those who feel it is a bit grim. But I don't think anyone needs to not go to sessions because of the directness. Just follow a few reasonable guidelines. These aren't rules, but I suspect will help you get involved with sessions of any sort.
1) Go to listen at least once, and maybe more times. Don't plan on playing, and perhaps don't even bring an instrument. Listen to the tunes and figure out if you know enough of them and can play them at the session tempo.
2) If you can't play up to speed or don't know many of the tunes get some sort of recorder, GET PERMISSION to record things and go home and learn. If the group is just too advanced ask members about other sessions. Be honest about your level. You'll get help.
3) Do your asking (recording or other sessions) at times when playing has actually slowed down and don't interrupt the flow of things.
4) Limit your questions about titles. You can always learn them later and constant asking will be viewed as an interruption by some folks.
In sum: Remember that they are there to play music and stay out of their way.
5) If you decide you can keep up and have many of the tunes it is polite to ask if you may join in. Or, to bring an instrument and sit back a bit from the regulars and try to play without being in the spotlight. If you play OK you'll be asked to move into the circle or space will be made for you when you arrive (depending on the space in the venue of course).
6) If you go to play be sure you have at least one tune (or set if the session plays sets of tunes) you can lead. Sooner or later you will be asked. No one is trying to put you on the spot, they're just being polite. And, that's a way for everyone to discover how you fit in. So, be prepared.
7) Unless you know the session welcomes sheet music and music stands don't bring any.
If you play guitar learn chords and watch others for chords you might be missing. Some sessions limit guitar to on player at a time. That's because too many guitarists think they are playing a string bodhran. Even if you play good guitar try to learn a bit about Irish guitar playing.
9) If you play bodhran don't play if another player is playing. I don't know how you handle those who won't give you a turn.
10) If someone speaks bluntly to you try to understand what they are saying and be aware that it is intended to be helpful despite the way it sounds.
Now, none of these thoughts are fixed in stone. They really boil down to being sure you belong in the session from your perspective and from that of the others. Sessions are groups of friends and like any social group you need to work your way into it, not come and assume you fit.
So, do go to those sessions. Just be thoughtful about how you do it.