TLDR: A good series that scratches a certain niche but can be hard for everyone to enjoy. No the ecchi content is not bad.
My Dress Up Darling is a good series but tends to get a bad wrap from people who can't relate to the themes or hyper focus on the ecchi content. If you enjoy romance, cosplaying, themes of self expression, and watching characters grow to achieve their dreams you should give it a try.
-Romance-
A decent romance series that does a good job at building up the relationships between the characters. It's a lot more prevalent compared to the ecchi content, but still lacks in comparison to the thematic and cosplay content.
-Cosplaying Niche-
There is a heavy focus on cosplaying. It does an amazing job at diving into why people enjoy cosplaying and the process of putting a cosplay together. It goes especially in depth on a lot of cosplay tricks and can 100% teach you new stuff. If you enjoy cosplaying you will have a lot to relate with in the series and defiantly need to give it a try.
-Themes-
Several somewhat complicated themes are expressed in the series. For example, there is a heavy emphasis on "self-expression" and "sharing your interests". Gojo is a timid guy who is afraid to express his interests in doll making because he doesn't want to get made fun of, while Marin is outgoing and loves to talk about her favorite series. As the series progresses more characters are introduced and have different ways of expressing or having issues with expressing themselves.
-Character Growth-
Several characters grow and develop throughout the series, but Gojo does the most. From the beginning we are introduced to Gojo's dream of becoming a doll maker and as the series progresses we get to see him hone his craft and creep closer to his dream. It is also refreshing to see him break out of his comfort zone and build relationships with new people.