LISTEN UP IF YOU'RE THE LAST PERSON I AM ABOUT TO CHANGE YOUR LIFE
When I was younger, etiquette dictated that a dish taken to someone's house for a form of bereavement (death, divorce, job loss, etc.) should be nice but understated--china, but no loud or overly cheerful patterns. There were no limits on dishes taken for celebration, but it was generally accepted that you shouldn't use plastic because of the risk it would stain in the recipient's dishwasher, and then joy would turn into stress. (Dishes that stained that way were also a lot more common back then.) It wasn't rude to use plastic, but it was considered nice to think ahead.
Ain't nobody got time to wash a fucking casserole dish when they have two jobs and a funeral to plan and the days of most of your friends being Right Next Door are gone.
These are cheap as fuck and you can get them everywhere. Walmart. Amazon. I get mine at the local grocery store. They fold directly into the trash. If you want to get fancy you can rinse it and it recycles (in a lot of places--check your local rules). If you have a friend with special dietary needs these can double as a prep space because they're not already cross-contaminated.
I recommend these for bereavement. For celebrations, I keep what I call pass-forward plates--I'll find a couple of cute mismatched plates at Goodwill, and when celebratory food is called for I use those plates with the instruction that you can return it to me if you're really that pressed about it, but you're more than free to keep it...and pass it forward with the same instructions.
I have only ever had one pass-forward plate come back to me. People love them and they love knowing they can just...toss it in the dishwasher when they get to it.
GOOD DISHES FOR BEREAVEMENTS:
--one-pan dishes (e.g. pot roast, chicken and potatoes in sauce)
--pasta with sauce (make Alfredo for your friends, it's five ingredients and fifteen minutes)
GOOD DISHES FOR CELEBRATIONS:
--baked goods (cookies, quickbreads, cupcakes, etc.)
--fruit salad (in summer)
I strongly recommend doing in-home foods. Sometimes you don't have the strength for an app. When my sister's FIL died the family was sitting shiva and I called a restaurant literally across the country that did catering, and got them soup. My sister had insisted it wasn't necessary until the soup came and everyone went "oh thank G-d, none of us wanted to face picking food." They didn't even have leftovers, and that was with me ordering extra on purpose. Everyone was just glad someone else had made the decision and they didn't have to think.