I started building speakers in 2005. I think DIY is generally worth it, but there is some fine print to it. From my personal opinion, DIY speakers will provide you with an acoustic performance that is 2x or 3x the price compared to the retail market. That said, the cost of tools and for finish need to be considered.
When I started out, there were no online carpenters who would send CNC machined baffles for cheap. You needed a router, and most importantly carbide/hard steel router bits to cut plywood or MDF consistently. Good bits often cost as much as the router itself and the cost can easily amount to a sum that would afford multiple of the cheaper DIY speakers kits available. So unless you're gonna build a lot of them, and/or you got the tools anyway, acquiring them is not worth it for a single speaker pair. At the lower end of the price spectrum, you're not gonna compete with retail products. I cannot DIY a desktop system with subwoofer for 150$.
Nowadays, despite having the tools I no longer bother cutting things myself, there are so many good online options to get things cut via CNC that I don't wanna bother with the noise and the dirt anymore. I simply design all protruding edges 1mm over spec and then use a flush trim bit, or simply order all boards prepared with lamellos and then it's just like lego.
The finishing is a topic where a lot of the cost can end up, or not. My inital 2x, 3x retail price statement was based on raw speakers. If you want a finish that is as good as retail/highend speakers, it will be either impossible with DIY, or cost a lot of money. I've tried painting things myself, and I'm not gonna do that anymore. The time invested and the stress is not worth it, you will not get a result that is on par with retail/professional products. Just look at the KEF LS50 for example. Good luck replicating that yourself in your garage.
Another topic is veneering. Smaller speakers you can veneer yourself, but when the speakers become bigger than the stem of the tree, things get interesting.
Where DIY is really worth it IMHO is subwoofers. They are often hidden/not as visible, and the retail prices charged are really high. All my subwoofers I ever had were DIYed. Since the speaker only operates around its resonance frequency you can use free of charge simulation tools and end up with something that makes sense. Since the room takes over below Schröder anyway, you don't need fancy measurement equipment but simply adjust to taste.
Long story short, if you expect retail look and finish, then it's not worth it unless you're building a lot of them. Good kits might make this viable, but in general just for a single pair, I wouldn't bother. That said, it's a nice hobby. Whatever you build, music is gonna come out of it, and it makes you happy. For kids this can be a lot of fun, and there's a ton of really cheap options available.
e: Another thing to mention. There's a ton of exotic speakers that are not represented in the retail market, like horns or transmission lines. I started out DIYing with fullrange speakers and they're a ton of fun but almost non existent outside DIY.