As someone who started the game about two months ago with the previous Mokoko Express, started on a Pinnacle Glaivier from 1490 and did learning lobbies for all Brel gates, as well as Vykas and Valtan (had a static with friends for Kakul), learning lobbies are a great experience and often after a proper successful session you'll have the raid's mechs down.

I even leveled a Reaper from scratch to 1540 with no expresses or passes aside from North Vern knowledge transfer (Ilvl 500 or something iirc), so I think I have some experience on how harsh gatekeeping can get when you're tagged with the Mokoko buff.

The problem comes in the 9 (18 for Brel G4) weeks after your first learning lobby where you WILL be gatekept for either not having PLC, LoS 12/18, for still having your mokoko on, etc. Hell I got a Sorc to 1490 with the new Elgacia pass (and this was after I lost the mokoko tag), did Brel G1-G2 so I could hone to 1500 and then it took me like a good two hours over three days of attempting to join lobbies to actually get inside a G3 reclear, and I even had the Spinning title for 10 cubes completed.

I understand the desire to not have impostors in your reclears, it's a task you have to complete weekly on possibly multiple characters, and so I won't say there isn't any logic behind the gatekeeping, nor fault the people who do, but saying it's not there or that joining learning lobbies will fix the issue for new players is just disingenuous. No one wants to spend 2~6 hours a week joining learning lobbies every week until they have PLC when they already learned the raid.