If you're planning on running DMs on IG, stay away from any niches involving crypto/finance/credit repair/etc. It is a complete waste of money nowadays. It worked amazingly in 2021 but now you are practically guaranteed to get a negative ROI running DMs in those niches. However, other niches can still perform pretty well, depending on the outreach strategy. Like the whole brand ambassadorship DM in the fashion niche is still making its rounds. Sales of marketing-related services can still perform well too. Mid-ticket adult offers, etc.
Yeah, the traffic may be getting more expensive but at the same time, that means there's less saturation. There's a reason why TG DMs worked better for crypto in 2022 despite costing 12x what 1k IG DMs used to cost. The people interested in crypto on Instagram were being sent like 2-3 messages per day about some new crypto/NFT project. Basically anyone that has ever even just liked a crypto post in the past had gotten a message because of how cheap and easy it was to send em out in bulk. At the end of the day, the more people get priced out of running this strategy, the better conversions will be for the remaining user base in the foreseeable future.