I have done some pro-GM work. It is interesting, but it isn't the same as running for friends/acquaintances, or even running at a con. It is a professional service and for me that sucks a lot of the fun out of it.
Aside from that: what is going on with Millenials* and GenZ* [EDIT] players entering the hobby now that they don't want to GM?
*Broadly speaking, as I assume those are the majority of new people entering the hobby.
I'm in my early 50s and have been playing since the early 80s. When I got back into TTRPGs with 5e I started going to local conventions have played in Adventurers League games off and on, often playing with new and younger players. Also my younger son plays with his friends. There has always been more GMs than players and the success of 5e, which has involved an influx of new and younger players indicates that there must be a lot of young players DMing. Anecdotally, the DM
layer ratio today is not any worse than it was in the 80s. Maybe things were different in the 90s and first decade of the 2000s. Don't know. I missed those 20 years.
I think that that the interest in professional DMs has more to do with the increased popularity of the game, increased and continued interest from those who are well into their careers and have more money than time, and the increased availability and affordability of video-conferencing platforms and VTTs.
As a customer, I can explain why I'm happy to pay for a game.
1. I do DM. I run one 8-hour session about once a month with a group I've been playing with for six years. Even that can be challenging for me in terms of time, but it is important to me and I make it work. I can't DM any more than that.
2. I would love to be a player. But my work and travel schedule makes it very difficult to commit to any on-going campaign on a regular schedule.
3. I'm often in countries and cities that have no game stores, meetups, etc.
4. Even when I am, it is really a pot shot that their will be a game with an opening, at a convenient time and place.
5. I've used various find-a-game platforms. The only one I've had somewhat regular success with is Roll20's find a game feature. The games are hit and miss, but I'm an easy date. I just enjoy playing, trying new games, and am pretty good at reading the room and adopting my style to the vide and preferences of the GM and other players. But it can be frustrating to find one shots. Most GMs that are NOT doing it for money are looking for players for a campaign. When there are one shots, the free ones are hit or miss--many GMs flake out or there are not enough players. I've had the best luck for paid one shots. Players who pay for a session are less likely to flake out and GMs looking to get paid, even less so. Also, there are quite a few GMs that run free games that require you submit a short application and have an interview first. I don't mind answering a few questions to ensure shared expectations, but don't have the time or interest in being subjected to a job-interview experience. Most good GMs-for-pay write up a good pitch, what game they are running, any homebrew, whether they have pre-gens, enforced table etiquette, etc. And they might have a short poll when requesting a game that asks about your experience with the system, gaming in general, preferred play style, etc.
6. Many professional DMs have a series of adventures that they regularly run. Not only is this more cost effective for the GM in terms of investment in materials and prep time, but they are generally very well prepped for the game which makes it run smoothly. You don't have spend a third of the game waiting for the DM to read ahead or look things up. Also, they are more willing to invest in battlemaps, minis/tokens, sound, etc. customized for the adventure. Not at all needed for me to enjoy the game, but it is a nice touch.
Some things that I hope this service will provide that I've seen lacking in other systems:
1. More effective scheduling. Something like "Schedule Me" or similar sales/consultant scheduling platforms. There is too much e-mail and waiting in most find-a-game platforms.
2. More granular filtering for time (and time zone), language, system, VTT platform, style, etc.
3. Someway to work more prep/admin stuff into the game-slot selection. If you they have pre-gens, let you select them at the same time you are signing up is one example.
A nuisance with on-line games is VTTs. Even where the GM has a license that allows free player accounts, having to download, install, test, and learn a new VTT during a game can be a pain. This is a more difficult nut to crack. But it is a bummer with on-line game conventions having to limit which games you sign up for based on VTTs. I've been thinking that something could be done with VMs that you would give players access to, but for most GMs the cost and hassle wouldn't be worth it, but it is something a game-matching platform might be able to provide at a price point that makes it worth it for professional GMs. Barring that, my recommendation for professional GMs running online games is to stick with systems that do not require the player to download and install anything. Roll20 and Foundry are great for full-featured VTT. As much as I like Fantasy Grounds, I've had so many issues trying to play using it in certain countries that I just avoid any game being run on that VTT. Plain old video conferencing tools like Google Meet, Zoom, Discord, or MS Teams are often sufficient. I don't need a full-featured VTT to enjoy an online game, but I do enjoy seeing the battlemap for some games like D&D. Role (playroll.com) is a great compromise. It is primarily a video conferencing but is made for TTRPGs with charactersheet integration, a dice roller, and simple battlemap & token support. Very very easy to use, even for less-technically inclined players.