The entire year is always a good time and never too late for a person to wake themselves up to doing teshuva and begging forgiveness directly from Hashem.
Yes these days listed above of the yomim noraim are definitely more powerful days set up directly by Hashem as days for doing serious teshuva and returning to Hashem.
Even today THOUSANDS of years later it’s never too late for us to come together and do serious teshuva for the Eigel and for the Sinas Chinam that caused the bais Hamikdosh to be destroyed R”L