I’m not an advocate of HRM. I do use one (Garmin 305) but only to summarise my runs, to see where I’ve struggled or run well etc. It does give you a different insight into your running. Also agree that runners who have run for a number of years can run based on perceived rate of exertion. I also believe that technology can, when used appropriately, aid training if training is what you want. If it’s social just enjoy the run!