I think people massively underrate Jones and Smalling - two players who learnt from Rio and Vidic, and were coached by SAF. Sure, there have been injury problems and plenty of mistakes, but that's par for the course with defenders - it just happens.
Bailly has been here 5 minutes and has proven nothing yet. Lindelöf has also proved nothing. They both may turn out great,
they both might be shite. The only thing we know for certain is that Jones and Smalling are very good defenders, and assuming that two new young defenders will automatically take the starting spots is a little "grass is always greener on YouTube", imo.