Both of these shows share similar fatal flaws -- they've both been done better by someone else already. Re:Zero > Isekai Smartphone, and Chihayafuru > Nana Maru San Batsu. Leaving no real purpose for these shows to exist.
Unoriginality isn't the only problem with these shows though. The art is not up to par. Just compare the art to Princess Principal's. It just screams low budget, low effort, slapdash let's just throw something together. And the voice acting is atrocious. Especially for Nana Maru, I can't stand the heroine's voice. It's painfully bad. The hero in Isekai Smartphone is way too strong, robbing the story of all dramatic tension, but it's not quite a comedy either, so it really has nothing going for it.
With eighteen other summer anime and Game of Thrones to watch, there's no reason to settle for mediocre fare like this.