Question: In our modern time we see many Muslims don’t offer Salah for whatever reason. Moreover, on top of that they are engaged in many sins in the society, hence according to Shariah are they going to be regarded as ‘Kafir’ or still remains believer?
Answer: The person who regards the Salah as Fard and including other acts halal as halal, haram as haram and commits sin by falling in to the trap of Shaytan, then he or she will not be regarded as Kafir (infidel) therefore, still they remain Muslims. However, by abandoning the Fard Salah and committing other sins, he or she will be regarded as dangerous sinner and Faseeq. Thus, if Allah does not forgive his or her sins then he or she will face severe punishment in the hereafter. However, after the determined punishment he or she because of having slightest imaan, will enter the paradise at last. Allah knows the best.
References: [1] Surah An-Nisa (4:98) [2] Mishkat, 15 [3] Azizul Fatawa, 85, [4] Imdadul Ahkam, vol-1:41