I'm 29, been into the franchise on & off for roughly 20 years at this point. And yeah, I used to feel ashamed I guess, but always knew on a rational level that it's due to a gorillion issues I'm not gonna dive into here. More to the point, buying something nice just for myself at least once a month is basically part of my therapy; I used to feel bad about spending any money on myself.
I don't discuss this particular hobby much in fleshspace as it's really super niche here in Finland. Some of my friends (all of whom are older than me) are very into Pokémon Go and such -- things that somebody might call them childish over, y'know? But anime & manga + related hobbies & interests have become very commonplace over the years. And I mean, I remember when it was concidered weird for a 30-something to be actively playing video games. Now? I don't think I have a single friend around my age who doesn't play something at least semi-regularly.
I have a daughter, too. She's nine. And honestly, hanging out with her and sharing my interests with her & having her share her own with me really helped with getting over the weird, violent shame with which I was struggling for years. It really sucked cuz, I mean, who wants to be feeling bad about something that should be bringing them joy?
These days I'll have the vpet(s) I'm raising on me at all times. Sometimes I'll make it into an accessory, too. And I'm sure it must be kinda weird for some folks still, but I really don't care. Everyone's gotta have something. This franchise is one of the few good things I've had with me since childhood. It's a friend, basically. Comfortable and nice. And I love that.
If I'm coming across as childish to somebody for being enthusiastic about Digimon, that's their hangup. I've already dealt with mine.