1. Waseela is not Dua from anyone other than Allah. Dua is an IBADAT that can be done only for Allah. When one uses Tawassul in supplication, one does not ask and seek from other than Allah.
2. While explaining/for understanding Waseela the example of King and person closer to king, Example of ladder/steps to reach the building must not be used. These are dangerous example and not proper at all and will lead to deviated thought sometimes may lead to the Shirk. Allah power/his way of doing things should never be compared it is free from all
3. Allah always command for best way.As waseela is way of quran and sunnah. So chances for acceptance of dua is more with waseela. And we should seek waseela to increase the dua acceptance . Tawassul is not only permitted, rather recommended But it is not a compulsory thing for a dua to be accepted.
Allah himself has permitted and has asked to seek Waseela. That’s why we are seeking Wseela.
Allah Most High says:
يَا أَيُّهَا الَّذِينَ آمَنُوا اتَّقُوا الله وَابْتَغُوا إِلَيْهِ الْوَسِيلَةَ وَجَاهِدُوا فِي سَبِيلِهِ لَعَلَّكُمْ تُفْلِحُونَ
“O you who believe! Fear Allah and seek a means (waseelah) to him” (Surah al-Ma’ida, V: 35)
Allah Almighty says:
وَمَا أَرْسَلْنَا مِنْ رَسُولٍ إِلَّا لِيُطَاعَ بِإِذْنِ الله وَلَوْ أَنَّهُمْ إِذْ ظَلَمُوا أَنْفُسَهُمْ جَاءُوكَ فَاسْتَغْفَرُوا الله وَاسْتَغْفَرَ لَهُمُ الرَّسُولُ لَوَجَدُوا الله تَوَّابًا رَحِيمًا (64)
"If they had only, when they were unjust to themselves, come to you (Prophet, Sallallahu Alayhi Wasallam) and asked Allah's forgiveness and the Messenger of Allah had asked forgiveness for them, they would have found Allah indeed forgiving and Most Merciful". (Surah al-Nisa, V: 64)