they are large because they are modern versions. Or they got updated behind your back. I noticed once that even if I never set up Play Store, it still tried to 'update' specific apps, mainly Google apps. Even with updates turned off, they still update select apps, unless you disable download manager in system which breaks Play Store and is one of the first things I do on a new or used device.
CyanogenMod peaked at 7.1, based on 2.3 Gingerbread. Nothing Lineage makes even comes close to the level of deep customization baked into CM 7.1. Custom ROMs are mosly just unofficial updates at this point.
I still have my Nexus 6, which has VoLTE hardware support, but nobody makes a 2.3-based ROM for it. XDA laughed at the suggestion, even when I said I'd pay for development if needed. It's like everyone wants to forget that era of Android completely. Android today is a bad iOS clone. I mean, sure, I made a convincing imitation of Sense 3 + TouchWiz UX on my Z Flip 4, because Samsung bakes in a lot of stuff that comes closer to the baked in options in CM 7.1, but it's always going to be half done. I cannot get the Gingerbread lock screen, status bar style, or launcher UX.
How many people even bother with a Wii or 3DS at this point? Because a few devs managed to resurrect WiiNet24 and many of the built-in apps on the Wii, including Forecast Channel, multiplayer backend, and Everybody Votes, and on the 3DS they resurrected MiiVerse, muliplayer, the friends system, EShop, and much more in homebrew. The 90s internet is able to be browsed from a Windows 95 PC running Internet Explorer 5 for crying out loud thanks to the Old Net. So why can't I use Android 2.3 today? Or have someone bring back Android Market since it's not Google's but open source in the first place? I think it would have been great to have F-droid use Android Market and its UX for a front end. That's no different than having eshop back on 3DS because it just redirects the requests to a spoofed API that makes the app think nothing has changed.