This film seems to be either love it or hate it, and I totally understand both.
The movie touches on relevant fears of today's economy by exploring the default heteronormative life plan sold primarily to young couples as mundane and unfulfilling. It portrays the idealistic white-picket fence as unattainable and, even for those who achieve some semblance, far from a guarantee for happiness.
We see more taboo topics broached as well, including unwanted parenthood and the subsequent emotions in the unique ways mothers and fathers might experience it different from each other. The Jekyll and Hyde of trying to bond with then being repulsed, the outright anger at being trapped, the complicated destructive impact on romance, sex, and simply being intimate are all explored. Developing addictions, violence towards women who blamed for being more sensitive, and trauma bonding are seen as well. Unlike other movies, this doesn't end with a "it was all worth it in the end" feel-good ending. It ends with the realization that this was a terrible mistake that sucked the life out of you and ruined every chance at happiness. This makes people feel uncomfortable because it's such a socially unacceptable way to feel about becoming a parent.
Some of the less worthy aspects include the alien species itself as it conflicts with the other themes (unless it's going to the next generation feeling foreign to the parents, but that's a stretch), and the no way to escape except death aspect that reminds me strongly of 1984. Ie. Don't let this happen because we will never escape if it does.