Clubs always need new members to make up for the people who give up caving for one reason or another, and they accept that for every half dozen new members who turn up and try a few trips, perhaps only one will enjoy it enough to stay long term.
Most clubs have some form of provisional membership as well as full membership, and they'll let you go on one or two easy trips before expecting you to join. Don't be afraid of trying two or three clubs to find the one that suits you. If you do run into a club where you feel you are 'holding back the keen cavers' then it's not the club to join - there's plenty who will make you feel really welcome, suggesting suitable trips and later on helping you to learn rope techniques. From your side, you may need to be a bit patient - a smaller club may only run one or two trips a month, and you may need to wait for a few weeks for a suitable trip.