Trees are a way to temporarily store CO2. If you just plant a massive forest and do nothing else, today's trees will eventually die, rot, and re-release all that CO2. That forest will regenerate itself if left alone and be a store of CO2, but any individual tree is lifecycle approximately zero.
I mean you're not wrong, but if we take that view the only permanent solution if to capture the CO2 and stuff it back into the ground, preferably as a relatively stable substance such as coal or oil.
Most of the worlds large forests are no more, many European countries are stripped of their old forests, so replanting those are required anyway, for other environmental concerns. They could on a permanent basis capture some percentage of the CO2. It is permanent if you view it as a forest and not individual tree.
> if we take that view the only permanent solution [is] to capture the CO2 and stuff it back into the ground
I think that's basically correct on the scale that's needed. I don't even think turning trees into building materials is enough.
Planting a lot of trees and letting forests grow has the advantage that it's obviously possible with current tech, while the forest is expanding in mass that CO2 is being scrubbed, and it's conspicuously visible to people (garnering feelings of goodwill and participation), but I don't believe the relatively small amount of incremental forest that we could reasonably create will make a meaningful change on a 100-year basis.
I think there’s some stats about the amount of co2 captured by planting an absurd amount of trees is pretty negligible
There are other reasons to plant trees (well, plant plants in general), notably around rehabilitating land that is on the verge of desertification or the like.
Trees also cool their environments through evapotranspiration as well as literally converting sunlight into sugars. There's more benefit than just carbon capture per se.
To be fair, all other carbon capture technologies are still net-positive emissions-wise, after accounting for (what's typically dismissed as mere) externalities. The fact that trees, ie forests, are net-negative and also have other benefits (QoL for lots of organisms, increased biodiversity leading to resilience, etc.) puts them at the top of the list in this category for me.