I'll gladly deal with any downsides if that means maintaining the principled standpoint that being a member of society doesn't require owning either an Android or IOS smartphone, being forced to run someone's black-box proprietary software, and agreeing with some foreign mega-corporation's dubious terms of agreement. It's harmful for democratic society as a whole to engender such a dependency.
Besides, if the experience of friends and colleagues is anything to go by, opting in to Whatsapp means you get its downsides too: that one group member who keeps spamming everyone with noise, the constant demand for attention, the gossipy, sometimes down-right stalkerish neighbourhood watch groups (glad my neighbourhood hasn't hung up those sycophantic Whatsapp street signs), not to mention Facebook looking over your shoulder at the metadata level.