I've been out of the loop for a few years. Back in the day, I was advised to purchase .com, .net. and .org if I ever wanted to develop a domain name /brand.

So mydomain.com, mydomain.net and mydomain.org

Is this approach still necessary /advisable?

I think people would develop one of these and have the others redirect to the main one.

Thanks for any feedback!

Yep. Still good advice today. You might consider .biz and .info as well, if you're protecting your brand. You might also consider singular/plural and hyphenated names as well.