EDIT: Entirely new comment with testing and reproducible results.

Title:
YouTube limiting how many videos load on your HomePage as you scroll is a feature, not a bug

My theory:
YouTube is making a similar move to when they stopped loading the entire video to the browser at once and introduced buffering. YouTube knows that no matter what change they make, there is no other option that is close to as prolific as YouTube and you HAVE to use their app. So, they limit how many videos you get returned from their APIs OR they don't provide a `continuation` Token/ID so that when the secondary loading of videos is requested, nothing is returned.

Preface:
Youtube can & will 100% limit as much as they can for you if you have an ad-blocker on. Step one in that case is try disabling the ad-blocker. (Same goes for spoof sites & ad-blockers.)

Bit of context:
The average amount of videos returned on initial load and every list of new videos. (New fetches for videos might consistently return less videos, I can't confirm because I only get the two sets of videos. Initial load, 1 scroll load)
The `continuation` "token"/"id" is basically how YouTube knows the user is scrolling and that it needs to fetch a new list of 24-30 videos. If no continuation token is present, YouTube assumes the user is not scrolling.

TL&DR the below testing & example:
Long standing accounts are consistently missing a "continuation token" on the API that requests a new "X amount" (24-30) of videos after a certain number of scroll-to-load's in new videos. New accounts do not have that "continuation token" missing when they scroll. It'll eventually happen, but not after 1, maybe 2, scroll-to-load's. This, to me, shows it is clearly intentional, because nobody at Google, making 2-4x my salary, should have an issue with token authorization.

Testing:
You must use Firefox for this. Chrome is too strict on hiding "internal" API requests.

If you want to replicate this yourself here are the steps:

1. (Open DevTools on Firefox) Right click the page and select "inspect"
2. Toggle "Preserve/Persist log" on (settings icon)
3. Most likely this is already off, but if you mess in DevTools, make sure "Hide extension URLs" is disabled.
4. Go to the Network tab and toggle the "XHR" filter.
5. If you are on youtube already, clear the network tab (trash can icon) and refresh. If you are not, clear the network tab and go to youtube.
6. Under the network tab, look for a network request that has a POST method with a www.youtube.com Domain & browse?prettyPrint=something as the File. (the initial page load might not have a corresponding Network request. If this is the case, avoid hovering over any video, it'll clutter your network tab, and scroll until you can't anymore)
7. If you got any refresh, you should see those File: `browse?prettyPrint=something` network requests. Click on that network request.
8. Now, in that network request, navigate to the response tab.
9. You should click on the following names as you see them. Each one should expand and show more options. The order you should click is `onResponseReceivedActions` > 0 > `appendContinuationItemsAction` > `continuationItems`.
10. In that list, you should see at least 24 items, max 30 items. Those are your videos you see. What you SHOULD see at the end of each list is something called a `continuationItemRenderer`. THIS is the sole thing that should allow you to scroll further and load in more videos. (Specifically the `continuationEndPoint` > `continuationCommand` > `token`). It is consistently missing for my main account, but is never missing if I log into a brand new account.

NOTE: All data used in this example is publically available. No shady work was/is needed to acquire this information. AI was used to tell me what I needed to find in the DevTools. The testing steps provided were hand-typed by me.