First, if you wanted a kor cartographer effect in your deck, you probably wouldn't mind a 2nd. Secondly, I don't know - this is like saying that light up the stage is bad because jeska's will exists. Both sets of cards have a similar place in the decks that want those effects, but situationally each comparable card can be better than the other. This isn't comparing grizzly bear to scavenging ooze.
Yes, in the times that you get stuck on lands and can't cast Solemn and other 4 mana ramp/search this is good, but then you still have other 2 mana options that do the same, if not better. Maybe if it could look for any Plains rather than just basic it would be fine, but that basic really holds it back.
The issue with the card is that there are already options like that and they are better. Solemn Simulacrum, Knight of the White Orchid, Sword of the Animist, Weathered Wayfarer, and just a ton of mana rocks and other recent white land ramp/search.
Yes, in the times that you get stuck on lands and can't cast Solemn and other 4 mana ramp/search this is good, but then you still have other 2 mana options that do the same, if not better. Maybe if it could look for any Plains rather than just basic it would be fine, but that basic really holds it back.