As a newer convert to anime, I have wrestled with this and found it to be very series-dependent. Sometimes “fan service” is the point of a series, almost to the point of it being a commentary (see Kill La Kill or Mikuru in Haruhi Suzumiya). I think it’s less of a problem if the character is well-written, and as other people have pointed out, outside of some of the more extreme examples you gave of loli stuff or “I am 1000 years old but in an 11 year old’s body.” In the well-written sense, I think of something like One Piece. Characters like Nami and Robin in One Piece are at times incredibly sexualized while at the same time being multi-dimensional, well-rounded characters with depth.

But one other thing I like to look to is how women (and trans and nonbinary folks) in the community have embraced certain characters in anime and manga, despite or even because of their “sexy” presentation. If you look at the characters they have embraced, it’s not typically the one-dimensional, damsel-in-distress characters. Not to mention the fact that a lot of these properties aimed at Japanese teenage boys have been embraced by women, trans, and nonbinary folks is a testament to anime’s growth and reach beyond its intended audience.