Listen to me.
Happy endings are not bad.
Wanting characters to be ultimately happy is not the same ignoring conflict.
Writing good conflict WITH a satisfying and believable resolution takes time and talent.
You are a good writer even if you only write happy endings.
Grimdark sad endings do not have more depth than happy endings.
Anyone who tells you otherwise is probably a grimdark writer with a disproportionate sense of their own ability and depth.