I build my own landing pages. I don't believe landing pages matter.
Domain names are mostly sold via the registration path where marketplace listings are syndicated, e.g: a person searches "example" at GoDaddy and GoDaddy has "example.com" listed on Afternic then GoDaddy will promote the domain "example.com" to the registrant as a "premium" domain which they can buy now. Hard for domain name investors to accept, it seems completely illogical, but
most people do not visit domains they want to buy.
For the small minority of cases where a person decides on a domain name outside of the registration path, and visits the domain they want directly to end up on the landing page, the primary question is whether or not they can trust the purchase path. The purchase path is not dictated by the landing page, because a landing page can include many payment options.
People trust GoDaddy because it is a name they recognise, not because they have the best landing pages. As long as your landing page links to "buy via GoDaddy" then you get all of the benefits of GoDaddy without using their landing pages
I run various experiments, including a 50/50 split on domains to different landing pages (e.g: I'll compare GoDaddy vs. Spaceship) and my own. I have not observed any meaningful difference.
The levers you can pull to increase your sell through rate:
Distribution you need your domain syndicated to the registration path of as many registrars as possible (Use Afternic for GoDaddy, Spaceship for Namecheap, Sedo for Porkbun... etc.)
Price a domain listed for sale at $500 is much easier to buy than a domain listed at $5,000. However, lower prices do not increase demand: a domain that nobody wants is a domain that nobody wants at $500 or $5,000. Lowering the price means more of the people who want your domain can afford it but you still need to find people who want it.
I enjoy working on my own landing pages, I enjoy the analytics and the control, I can understand the behaviour of my visitors and experiment, I can identify why people are visiting the domain, and I can read emails too, all of which I believe is very valuable information. However, I don't think the content of the pages themselves matters much at all, because any purchase should be going through a reputable platform regardless of how the domain is found.