If the reported group speed is correct, this is an advanced group ride. My interpretation is that the OP is a relatively new cyclist.
I would actually advise not joining in these rides. You need to know how to ride in a group. This includes how to hold the wheel in front of you closely, which does mean trusting a stranger. It includes all the little etiquette points already raised. It also includes being to behave safely while under physical stress. A beginner rider might not be able to do all these actions when under a normal level of effort, let alone when they're barely hanging on.
If you're in this situation, it's better to search for organized groups near you that operate at your level. Many clubs operate sub-groups at a range of difficulties. For better or worse, you're not necessarily guaranteed a ride at your level. For example, one former club (the Potomac Pedalers in the DC area) are large and have (or had) a spectrum ranging from D or C rides (~15 mph) to A (around 20 mph on flats, about a US Cat 4 or higher level or somewhere in the Zwift B range). There wasn't a gap in that range, but faster riders would have wanted something else. My current club (Balance Cycling in Minneapolis) has a couple easier groups, a couple of intermediate groups, and a fast group. The intermediate groups are OK for a range of fitness levels, but I believe there's a bit of a gap between the top of the intermediate riders and the advanced groups. A stronger intermediate rider might still struggle on some of those rides - I've been dropped in the first few miles of some of the Thursday rides. The point is that you may need to shop around for a club that matches your current level, and that has room for you to progress if you desire.
Imagine that you are stepping up to a harder ride. In my experience, you can experience challenges physically and with bike handling (e.g. if they take corners fast). In addition, riders may draft closer than you are used to because it is a significant advantage and it's expected. Generally, prioritize handling your bike rather than signaling obstacles. There is redundancy in the group, and it would be better for you to maintain control of the bike rather than point out a hole, accidentally hit another pothole, and then possibly crash and take a few people down. Any technique challenges will also be occurring under greater physical load. If you take a turn at the front, feel free to pull for 10 seconds and then rotate to the rear - all sane groups understand that there's a spread of abilities and that some people may be able to hang on but not pull.
In particular, I don't know if the the front riders signaled the potholes but the OP missed the signal. If you hit a pothole, then yes, you are stuck hitting the pothole. It can happen, we try to avoid it, but you can’t always evade every hole. Experienced riders will learn to bend their arms to take a hit, and they experience less startle effect. However, groups will maneuver to avoid potholes. On rough parts of the road where there are too many potholes to avoid, the leaders would either plan a different route, or alert riders to brace ahead of time. Or if this was a race-like group ride and everyone is on their own, that's yet another reason that cyclists in the OP's position should not simply join in.
All the above paragraphs are not intended to convey elitism. Read them more like you will need some skills first, then you will be ready.