I'm not sure of his background, but it's safe to say he's making the same assumptions as everyone else, so his comments are just as valid as everyone else.
However, I do think he's off the mark in a few places. For example, technical debt - I'm not necessarily sure we're seeing the effects of that here. Halo 5 made conscious decisions about what features to use and not use - which he describes accurately. Those decisions were made to prioritise the frame rate above all else. However, Halo Infinite has made similar decisions to achieve it's frame-rate. That's not technical debt, that's just frame budgets and engineering. Technical debt occurs when you're blocked or restricted via technical decisions made previously that now, either in hindsight or due to changing circumstances, were effectively the wrong decisions to make. You're paying for the sins of what's come before you, so to speak.
To get more specific, you accumulate technical debt every time you put off fixing or improving something. Every time a coder has to introduce a hack or workaround, or an artist has to make a series of compromises, you're technical debt increases. As far as I can tell, Infinite isn't hampered by technical debt - they're not paying for decisions Halo 5 made. Rather, they just made the
same artistic and engineering decisions (60FPS on all platforms, open world, dynamic time of time, base Xbox One as target) and we're just seeing the result of that. They were quite capable of making different decisions, they elected not to.
That's not technical debt.
Now, the cynic in me says a few YouTubers have used this phrase because it was dropped in those negative 343i GlassDoor reviews, and it sounds like you know what you're talking about, so they go in on it.
However, his comments on image based lighting is generally pretty accurate. So, take from the video what you will.