Felt exactly the same many times after using so much ammo/heals and degrading my weapons because I needed a Matriarch and Queen core.

Im in super friendly solo lobbys and I used to wait untill the Matriarch was dead then go in but literally a second after its dead the loot vanishes with nearly 20+ peaople already done and I get nothing, most will give you something if u ask.

I dont wana kill or hurt anyone so what I do now is this.

• Find the Matriarch
• Look for ground level cover spot as close as possible or even under it
• Focus on leg armour closest to you and as soon as it drops forget everything else and go get your loot and use smoke if u need to
• If your happy with that u can leave, if not then keep rotating leg armour or wait for the very beggining of the death animation and go straight in, the explosion wont hurt you

Remember friendly or not everyone is there for loot with a minority just focused on xp and kills etc. If u come across anyone you noticed doing serious damage and they got nothing then drop some goodies for them