I wanted to object to this action but I was afraid of causing trouble and I did not have sufficient evidence.
Was I sinning by being present and listening to their recitation?
Should I have objected to them, even if that was by saying that there is no proof of this from the Prophet (blessings and peace of Allah be upon him)?.
It is not permissible for the family of the deceased to make food and invite people to come and eat. The Prophet (blessings and peace of Allah be upon him) forbade that. Jareer ibn ‘Abdullah said: We used to regard gathering with the family of the deceased and making food after the burial as coming under the same heading as wailing.. Narrated by Ahmad, 6866; classed as saheeh by al-Albaani in Talkhees Ahkaam al-Janaa’iz.
It is not permissible to go to these meals and gatherings; rather what must be done is to tell people not to do that and to explain to them that it is contrary to Islam.
With regard to reciting Qur’aan together, if the group starts to recite Qur’aan together in unison, this is another innovation; this was not narrated from the Prophet (blessings and peace of Allah be upon him) or from any of his Companions.
This has been discussed previously in the answer to question no. 4039.
Based on that, you should not have attended this gathering and if you did attend, then you should have explained to them that this action is not prescribed in Islam. If they did not respond to you then you should have left the place, because the Prophet (blessings and peace of Allah be upon him) said: “Whoever among you sees an evil action, then let him change it with his hand [by taking action]; if he cannot, then with his tongue [by speaking out]; and if he cannot, then with his heart – and that is the weakest of faith.”
Narrated by Muslim, 49
Part of objecting to evil in the heart is leaving the place where it is happening.
See also the answer the question no. 96662
And Allah knows best.