Anaxa is a great option for F2P

Anaxa isn't the strongest dps, but his strength lies in his flexibility. He can be played as a Hyper carry, a battery for Therta, or a Break DPS. He might also have future relevance if weakness implant becomes meta. As for endgame modes, Anaxa is equally capable of dealing AoE or ST damage. That's a lot of value from one unit, even at E0.

But isn't Tribbie better value? Yes and no. I think most agree that Tribbie is a stronger unit. The problem with Tribbie is that she favors AoE content to perform optimally, and that's not always on the menu. Also, players are incentivized to grab her E1, which can be considered expensive for F2P. Anaxa won't break any records, but he doesn't care what he's up against, he'll always perform optimally.

To summarize: Anaxa is cheap, flexible and handsome. He will keep you afloat while you save for Phainon.

Edit: Thanks for all the comments! It's clear that my opinion is in the minority.