20. Disney Immersion
I think I understand what Disney visitors mean by immersion. They enjoy being within Disney themed areas during their entire visit. This includes hotel, transportation, shopping and dining, as well as the parks. This experience sort of blocks out the outside world and gives a more enjoyable Disney experience.
Immersion in this sense is more possible at WDW because of its large size which allows the outside world to be more thoroughly blocked out. The 20 Disney hotels also help. The setting at DLR is different. The parks, resort hotels, and DTD are in the middle of Anaheim, California. When you enter the DL park you will find the outside world fairly well blocked out. In fact I can never remember noticing the outside world when inside DL. DCA, for better or worse, was not designed this way. Perhaps the reason is that it would seem odd to design Disneys California Adventure and locate it in California, and then try to block out all of the surrounding real California. So DCA does not seem as isolated as DL. In addition, the DLR hotels look out on the city of Anaheim (in addition to DLR) and are not as isolated as at WDW.
The bottom line is that it is just not possible to have the same level of immersion at DLR as at WDW. By staying at a DLR hotel and taking the monorail or walking to the parks through DTD you will come closest.
However, there are some upsides to the DLR geography that may balance this out. The issue of transportation and hotel locations at DLR have already been discussed and will not be detailed again here. But note this - when one stays at a DLR hotel or certain Good Neighbor hotels, you can see the parks right out your window and easily hear (and see) the fireworks at night. In fact, if you are trying to sleep they may wake you up. You are right there, across the street from the parks. Although you are not immersed in Disney as at WDW, you nevertheless feel very close to the parks because you are. When you walk out your hotel room you may clearly see the Matterhorn or Space Mountain at DL, or the Tower of Terror or California Screamin at DCA. As also mentioned previously, DLR usually has longer park hours than at WDW. If you use the close hotel locations and longer park hours to your advantage, you may sense a different kind of immersion where you are in the parks for most of your waking hours and not waiting for or sitting on buses, boats, etc.
In summary, DLR does not offer quite the same immersive experience as WDW. But the fact that you can spend up to 50% more of your daily hours actually in the parks and have a room literally across the street from the parks can be immersive in a different sense.