Does Tawasul/التوسل or intercession contradict with the fundamental theistic principle of Islam?

The most fundamental principle of Islam is theism, that there's no God but God/Allah and He's solely should be worshiped and all other things are His creatures and slaves including His Messenger Mohammad. All Muslims regardless of their sects (Sunnah, Shia, Sufis, etc ..) believe in that. However, some Muslims do 'Tawasul (توسل)' which is pleading and begging Allah to fulfill the prayers for the sake of certain things or people, other Muslims ask Allah indirectly through the Prophet or the Prophet's household or other sacred people. Is Tawsul/التوسل or asking Allah indirectly through someone else contradicts with the fundamental theistic principle of Islam? Is it like associating partners with Allah (Shurik/شرك)?

إِيَّاكَ نَعْبُدُ وَإِيَّاكَ نَسْتَعِينُ
الفاتحة : ٥

You alone we worship, and You alone we ask for help.
Quraan 1:5

وَأَنَّ الْمَسَاجِدَ لِلَّهِ فَلا تَدْعُوا مَعَ اللَّهِ أَحَدًا
الجن : ١٨

And [it has been revealed to me] that the places of prayer belong to God, so do not invoke anyone along with God.
Quraan 72:18

وَيَعْبُدُونَ مِن دُونِ اللَّهِ مَا لاَ يَضُرُّهُمْ وَلاَ يَنفَعُهُمْ وَيَقُولُونَ هَؤُلاء شُفَعَاؤُنَا عِندَ اللَّهِ قُلْ أَتُنَبِّئُونَ اللَّهَ بِمَا لاَ يَعْلَمُ فِي السَّمَاوَاتِ وَلاَ فِي الأَرْضِ سُبْحَانَهُ وَتَعَالَى عَمَّا يُشْرِكُونَ
يونس : ١٨

And they worship, besides God that which can neither hurt them, nor profit them; and they say, 'These are our intercessors with God'. Say: 'Would you tell God of what He does not know in the heavens or in the earth?' Glory be to Him!, and High be He exalted above what they associate!
Quraan 10:18

أَلا لِلَّهِ الدِّينُ الْخَالِصُ وَالَّذِينَ اتَّخَذُوا مِن دُونِهِ أَوْلِيَاءَ مَا نَعْبُدُهُمْ إِلاَّ لِيُقَرِّبُونَا إِلَى اللَّهِ زُلْفَى إِنَّ اللَّهَ يَحْكُمُ بَيْنَهُمْ فِي مَا هُمْ فِيهِ يَخْتَلِفُونَ إِنَّ اللَّهَ لا يَهْدِي مَنْ هُوَ كَاذِبٌ كَفَّارٌ
الزمر : ٣

Surely to God belongs pure religion. And those who take besides Him patrons, [say]: ‘We only worship them so that they may bring us near to God’. God will indeed judge between them concerning that about which they differ. Truly God does not guide one who is a liar, a disbeliever.
Quraan 39:75

وَإِذَا سَأَلَكَ عِبَادِي عَنِّي فَإِنِّي قَرِيبٌ أُجِيبُ دَعْوَةَ الدَّاعِ إِذَا دَعَانِ فَلْيَسْتَجِيبُواْ لِي وَلْيُؤْمِنُواْ بِي لَعَلَّهُمْ يَرْشُدُونَ
البقرة : ١٨٦

And when My servants question you concerning Me, I am near; I answer the call of the caller when he calls to Me; so let them respond to Me, and let them believe in Me that they might go aright.
Quraan 2:186

First glance at the Quranic verses above would lead us to think that asking Allah through someone else is anti-theistic and it's like associating partners with Him as the pagans and idolaters used to do. However, if we ponder the verses again we would notice that the verses were referring to 'worship' and associating partners to Allah but that's not the same as Tawsul/توسل or asking Allah indirectly through some people.

قَالُواْ يَا أَبَانَا اسْتَغْفِرْ لَنَا ذُنُوبَنَا إِنَّا كُنَّا خَاطِئِينَ
يوسف : ٩٧

[His sons] answered: "O our father! Ask God to forgive us our sins, for, verily, we were sinners."
Quraan 12:111

وَمَا أَرْسَلْنَا مِن رَّسُولٍ إِلاَّ لِيُطَاعَ بِإِذْنِ اللَّهِ وَلَوْ أَنَّهُمْ إِذ ظَّلَمُواْ أَنفُسَهُمْ جَاؤُوكَ فَاسْتَغْفَرُواْ اللَّهَ وَاسْتَغْفَرَ لَهُمُ الرَّسُولُ لَوَجَدُواْ اللَّهَ تَوَّابًا رَّحِيمًا
النساء : ٦٤

And We did not send any messenger except to be obeyed by permission of Allah . And if, when they wronged themselves, they had come to you, [O Muhammad], and asked forgiveness of Allah and the Messenger had asked forgiveness for them, they would have found Allah Accepting of repentance and Merciful.
Quraan 4:64

The Quranic verses above clearly indicate that it is permissible but rather recommended to seek forgiveness from Allah through sacred people like the Prophets.

Moreover, there are several Hadiths demonstrate that Tawsul/توسل is permissible and Muslims usually do it in crisis when their direct prayers don't seem to be fulfilled. Herein an incident:

حدثنا ‏ ‏الحسن بن محمد ‏ ‏قال حدثنا ‏ ‏محمد بن عبد الله الأنصاري ‏ ‏قال حدثني ‏ ‏أبي عبد الله بن المثنى ‏ ‏عن ‏ ‏ثمامة بن عبد الله بن أنس ‏ ‏عن ‏ ‏أنس بن مالك ‏ ‏أن ‏ ‏عمر بن الخطاب ‏ ‏رضي الله عنه ‏
‏كان إذا قحطوا استسقى ‏ ‏بالعباس بن عبد المطلب ‏ ‏فقال اللهم ‏ ‏إنا كنا نتوسل إليك بنبينا فتسقينا وإنا نتوسل إليك بعم نبينا فاسقنا قال فيسقون ‏

صحيح البخاري : الجمعة: سؤال الناس الإمام الاستسقاء إذا قحطوا

Anas ibn Malik narrated that whenever there was a drought, 'Umar ibn Khattab used to pray for rain through 'Abbas ibn 'Abd al-Muttalib, saying: 'O Allah, we used to make Tawassul to you by our Prophet and you would send us rain. Here we are making Tawassul to you by the uncle of our Prophet, so send us rain.' He said and they would be given rain.

Sahih Al-Bukhari

Obviously according to the Hadith, Tawsul is not only permissible but is necessary especially in crisis. However, there's an argument of whether a Muslim can do Tawsul through a dead person. According to my research, the majority of scholars (Sunnah & Shia) decree that it's permissible to do Tawsul through the Prophet whether during his life or after his death.