Zoom's privacy policy gives them the right to share your personal data with 3rd party marketing firms
No it doesn't. They specifically say that they don't sell your data and will not share it without your consent. However, if you join a webinar you are providing your data to the host of the webinar.
Zoom's app for IOS shares your data with Facebook
They've fixed that.
Zoom's meetings can be gate-crashed by people who have found the meeting ID of open meetings
True, as noblegiraffe reports. It is too easy to zoombomb a meeting.
Zoom comms is not fully end-to-end encrypted
Also true. Furthermore, their encryption is not particularly strong.
The Zoom installer for MacOS uses a misleading prompt to gain 'root' access to Macs without actual consent. The installation process could be hacked to take control of your camera and microphone
They fixed this a couple of days ago. The researcher who found the vulnerability says he is impressed with the new implementation.
Zoom chats are vulnerable to attack by malware which can send your username and password to the hacker's machine, or execute malicious code on your local machine
Also fixed.
There are definitely security concerns about Zoom. They seem to be working hard to fix them, which is why some of the information in the previous post is out of date. I wouldn't use them myself as I think there are better implementations available.
I agree with noblegiraffe that, whatever conferencing system is used, there needs to be a proper risk assessment. Under the current lockdown, strange adults being in the room with the child is much less of an issue than it would be at more normal times. But there are plenty of other reasons to be cautious.