Because it's not just for old games. You seem to keep saying that. Forza Horizon 5, Apex Legends, Halo Infinite, The Ascent and a massive gamut of games I and family/friends all enjoy with Series X booting faster, running smoother, quick resuming and playing across devices such as PC, mobile apps and xbox consoles (One, One X, Series X). I see these games and apps across 3 generations of Xbox consoles in our house and I can hands down tell you I'm happiest with my Series X and its refinement and performance. I have titles like FH5 that just blow away graphics with that next gen feel, you seem so devoted to. I have games like Apex that outclass my mid-range gaming PC or son's One X etc. To me the next generation is a refinement of backwards compatible games, cross gen games, full next gen games and the features combining within overall ecosystem to deliver a grand slam homerun. We use a parenting app between my wife and I, cross-devices play with kids and gamepass bringing it all together is an amazing evolution of our gaming. By comparison to just the One X even, let alone by comparison to my PC as well. You're also short selling BC features of Series S/X consoles, old games run better and smoother while looking the goods as well. Further you're short selling the importance of PS5/Series S/X going SSD, it evolves everything from apps and UI to games and features.
This generation isn't so much a revolution as say N64 (3D) or PS1 (CD-ROM) or Xbox OG (online) or PS3 (blueray) or 360/One (apps) it's an evolution and refinement of everything gaming. Do I agree with you that full next gen only game releases are lacking in number at the moment? Sure, yes I do. Do I agree that diminishes my love of these new generation consoles as your posts imply or I should stick with previous gen consoles? No I do not. I refuse to believe you could run as much as the current gen Series S/X with emulation, BC, gamepass, cross-play/saves/sharing, accounts/achievos and more such as simply switching between netflix, then FH5, then my daughter logging in, my wife reviewing what my son played or hours played or son chatting with friends via his mobile xbox app etc. The evolution of this generation is a major refinement that will only improve as more next gen only games release over time. There are games coming that will be PS5 or Series X only too.