They have no importance for SEO.

Web 2.0 sites are not much of a help. If you want good links then try customized PBN's.

I've had luck with expired web 2.0s, never tried just 2.0s.

Web 2.0's have been ABUSED in the past to game Google's search algorithm with poorly written content pages used as link farms.

There's absolutely no reason to do that. It's a total waste of time. If you do outreach and find guest posting opportunities, some of them will naturally be active web 2.0's.

Links from active web 2.0 properties that are maintained by a real blogger are good links. Creating your own web 2.0 and posting low quality content is a bad practice that might land you a penalty.

It's generally considered a bad practice to "use web 2.0 sites to rank". Just do outreach. Most (not all) manual link-building is just a waste of time.

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Thanks all then what should be the alternative for web 2.0?

Advertising is very important for your site or product. where web 2.0 works great. google now don't considered spam completely. if you set up your keyword and back-links correctly then a web 2.0 will be very useful.

Use web2.0 should links to your PBNs, rather than directly to your money site. It's still working, but you should maintain your Web 2.0; keep updating on regular basis.