I think large age gaps can work, but you have to depict the difficulties of being in a relationship with an age gap sensitively and be aware of the issues, especially when the younger person in the relationship is under about 25. The best ones I've seen really wrestle with the issues of the characters being concerned about the power dynamics, whether they can really work and how society will see them, but ultimately manage to sell the idea that these characters really are a good match even after addressing every concern somebody might raise about why they shouldn't be together. They also generally have some way of making the characters not have a power imbalance, for example by making the younger person more socially or financially powerful and more confident.
There is an element of responsibility on the writer's part if an age gap story features a teenager (yes, even eighteen or nineteen) with somebody older to teach potentially teenage readers about dangers to look out for. Teenagers often get into relationships with older people where there's a really unhealthy power dynamic simply because the teen doesn't have the experience to recognise red flags or to know what's "normal" in a relationship and what's abuse or control. They're often flattered by the attention of an older person, thinking it's a sign of their own maturity compared to their peers, but not thinking through the ramifications of why somebody in their thirties isn't dating people their own age. Sadly there are people who date younger people because they're an immature mess nobody in their thirties wanting a stable partner would ever want to stay with, or because they like a partner they can boss around, and they aren't actually accomplished or smart enough to feel like the more powerful one in relationships with most people their own age.
Predatory people often target somebody younger who will be easily impressed by stuff like them not living with their parents, having disposable income, maybe a car to take them to places they'd normally need to rely on their parents to visit, and exciting stories about adult experiences like travelling or having experienced college/university which to a teenager are all aspirational freedoms they wish they had and make that person seem really cool and grown up. They might not notice things somebody the predator's age would notice, like they're deeply in debt, their home lacks basic amenities or is dirty and crappily maintained like a student house (which is... an incredibly sad way for a thirty year old to be living), they're in a dead-end job and their knowledge or experience, while impressive to somebody with less than two decades of life experience, is actually pretty limited and they'll quickly run out of interesting opinions or start showing their ignorance in conversation with somebody who has lead an interesting life or is educated and experienced to a high enough level to know the person is actually just spouting rubbish but in a very confident tone of voice.
Fiction often irresponsibly glamorises pairings where the older important CEO treats the young secretary or PA or waiter or similar to a lavish lifestyle, keeping them almost like a pet. Hell, Twilight has elements of this, where the 200 year old Vampire who looks like a teenage boy starts dating a teenage girl who is drawn in by his confidence and relative maturity and the freedoms and protection him being a superhuman vampire offer and he proceeds to be extremely controlling. Of course creative freedom is important, but I personally think writers should be careful of what teenagers might be learning about relationships from their stories, since teens have limited experience and may well use fictional relationships as a template for what a real relationship should be like.