Roblox (NYSE: RBLX), the video game creation company that lets people develop and share games without any coding experience, went public via a direct listing on March 10. I was initially excited about this company, since its ecosystem was sticky and its growth rates were impressive. But my enthusiasm faded when Roblox ended its first trading day at $69.50. That was over 50% higher than its reference price of $45, and valued the company at $45 billion -- nearly 50 times its revenue in 2020. Image source: Roblox. That would already be a high price-to-sales ratio for a company with accelerating sales growth, but Roblox's growth will likely decelerate after the pandemic ends, since over half of its daily active users are children under the age of 13 who spent more time on their computers at home during the pandemic. Investors should also recall that Roblox was only valued at $4 billion last year. Roblox's stock advanced to the low $80S earlier this month, but it subsequently dropped below $70 again. Those tepid gains over the past month indicate that the stock is stuck in neutral for now. But could Roblox still generate millionaire-making gains over the long term? What the bulls will say about Roblox Roblox's platform enables users to create video games with a simple block-based system. They can share their games and monetize them by selling additional in-game content or cosmetic upgrades for other players' avatars. Players make those purchases with Robux, its in-game currency. That self-sufficient cycle makes it more of a creator-powered social platform like Alphabet's (NASDAQ: GOOG) (NASDAQ: GOOGL) YouTube than a traditional game development engine like Unity (NYSE: U). That's why Roblox users also use YouTube to stream and promote their games. Roblox's revenue rose 56% to $508.4 million in 2019, then grew another 82% to $932.9 million in 2020. It generates most of its revenue in two ways: It keeps a cut of each Robux-based transaction, and it sells a monthly subscription plan that offers cheaper Robux purchases and other perks. Roblox's growth in daily active users, paid users, average bookings (which include its deferred revenue from Robux), and total engagement hours all soared in 2020: Metric 2019 2020 DAUs 17.6 million 32.6 million DAU Growth (YOY) 47% 85% Paid Users 184,000 490,000 Paid Users Growth (YOY) 47% 166% Average Bookings per DAU $39.40 $57.77 Total Hours Engaged 13.7 million 30.6 million Data source: Roblox S-1 filing. DAU = Daily active user. YOY = Year-over-year. The bulls believe that Roblox's momentum will continue over the long term, even if its growth cools off this year as more kids return to school. What the bears say about Roblox Roblox's revenue growth is impressive, but it's unprofitable. Its net loss narrowed from $88.1 million in 2018 to $71 million in 2019, but more than tripled to $253.3 million last year as its expenses soared. Image source: Getty Images. Roblox's infrastructure expenses rose as more people used its platform. More developers also converted their Robux back to U.S. dollars. Roblox buys back the Robux at a set exchange rate (currently at $0.0035 per Robux), and records those payments as "developer exchange fees". Those fees consumed 36% of Roblox's revenue in 2020, so it will likely need to reduce its exchange rate to narrow its losses. However, doing so could cause its top developers to leave. Roblox's high dependence on younger gamers and creators is also risky for two reasons. First, a growing number of inappropriate games are cropping up across Roblox's platform, which is forcing it to develop a new content rating system to make it easier to block those games with tighter parental controls. If those measures fail, Roblox's reputation could be tarnished and parents could stop buying more Robux for their kids. In its S-1 filing, Roblox admits that it has "faced allegations" that its platform "has been used by criminal offenders to identify and communicate with children and to possibly entice them to interact off-platform." Second, creators could graduate to more advanced game creation platforms -- including Unity and Epic Games' Unreal Engine -- after learning some basic skills in Roblox. That trend could limit the complexity of Roblox's creations and its appeal among older gamers. Above all else, Roblox's sky-high valuation and expectations for slower growth in a post-pandemic world make it an unappealing investment. Rising bond yields and the resulting rotation from growth to value could also exacerbate that pressure. Don't buy a promising company at the wrong price Roblox could keep growing, but it's already priced for years of unfettered growth at these levels. That's why the stock seemingly hit a ceiling earlier this month, and why it might underperform the market until it generates several quarters of stable growth in a post-pandemic world. Based on these facts, I can't consider Roblox to be a potential millionaire-maker stock. 10 stocks we like better than Roblox CorporationWhen investing geniuses David and Tom Gardner have a stock tip, it can pay to listen. After all, the newsletter they have run for over a decade, Motley Fool Stock Advisor, has tripled the market.* David and Tom just revealed what they believe are the ten best stocks for investors to buy right now... and Roblox Corporation wasn't one of them! That's right -- they think these 10 stocks are even better buys. See the 10 stocks *Stock Advisor returns as of February 24, 2021 Suzanne Frey, an executive at Alphabet, is a member of The Motley Fool's board of directors. Leo Sun has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends Alphabet (A shares), Alphabet (C shares), and Unity Software Inc. The Motley Fool has a disclosure policy.Source