Yes, NATO needs some reforms.
No, it's not obsolete at all.
I'm a peace activist. I believe that the United States should cut military budgets massively and should be far less interventionist. I believe that our foreign policy is illegal, colonialist, harmful, dangerous, and promotes chaos.
But Russia has demonstrated recently that it's perfectly willing to annex countries and is openly expansionistic. While I'd rather the United Nations have the strength to stop nations like Russia and people like Putin, I have nothing per se against security alliances outside of the UN.
The problem is that NATO has been a mechanism for US and Western power projection, which is wrong.
If NATO were to be properly modernized to be defensive and to not act as a power projection mechanism, as well as other appropriate reforms, it would be perfectly reasonable.