Those who could not benefit from Ramadan the way Allah commanded: Do not despair. All the months of the year, Allah is there!
If you have realised now, found time now- you can worship, you can seek to please Allah now!
Allah is waiting for your return every moment, every hour, 24 hours a day, 365 days a year, every year till you die!
You can sincerely Repent and make up the missed Fasts, read the Quran, pray Salaah regularly, do Dhikr, Supplicate to Allah, give Charity, adopt good manners- doing enormous good deeds is possible even after Ramadan.
Allah's assurance to us all:
قُلْ يَا عِبَادِيَ الَّذِينَ أَسْرَفُوا عَلَىٰ أَنفُسِهِمْ لَا تَقْنَطُوا مِن رَّحْمَةِ اللَّهِ إِنَّ اللَّهَ يَغْفِرُ الذُّنُوبَ جَمِيعًا إِنَّهُ هُوَ الْغَفُورُ الرَّحِيمُ
Say: O my servants! who have acted extravagantly against their own souls (by sinning), do not despair of the mercy of Allah; surely Allah forgives the sins altogether; surely He is the Forgiving the Merciful.
وَأَنِيبُوا إِلَىٰ رَبِّكُمْ وَأَسْلِمُوا لَهُ مِن قَبْلِ أَن يَأْتِيَكُمُ الْعَذَابُ ثُمَّ لَا تُنصَرُونَ
And return to your Lord time after time (repenting) and submit to Him (in obedience) before there comes to you the punishment, then you shall not be helped.
To the delinquent we say: make up, and to the outstanding we say: continue.