It depends on whether not the carbon offsets are verified.
For example by the American Carbon Registry, by the Climate Action Action Reserve or by the Gold Standard.
In this case Ecosia is a certified B corporation and the founder Christian Kroll has given up on the right to sell Ecosia or take any profits from the company.
No, all carbon offsets are greenwashing. A 0.0001% increase to the carbon absorption matters piss all when there's 2 million times that being released per second. The only real solution is to stop the engines producing the carbon. Remember the start of COVID when capitalism was put on pause for a few weeks? It's has been the only effective climate action ever implemented and it was done so by complete accident.
Search engines which are basically just middle-manning google except they plant trees have been a known grift for decades at this point.