What should a student of knowledge do if they've been studying for years but they find inability and weakness to establish basic sunnah worship like praying the Sunnan Ar-Rawatib and reading 1 Juz' of Qur'an a day? They still have the same sins and are losing hope that they will rectify themselves.

Subhana Allah, keep studying never stop. You cant read a juz' then read 10 pages a day. Start praying sunnah bit by bit. If you sin then you should be more encouraged to do worship to remove the sins as hasanat remove sins as Allah told us in the Qur'an, therefore don't understand it upside down that if you do some sins now u have to give upp all goodness and transgress more... this is not a healthy understanding.