While there's definitely something to be said in terms of relative scaling of budgets, Illumination is not in the same league as Blumhouse. Blum's approach is to produce a mix of semi-derivative "safe bets" (Truth or Dare, Happy Death Day) as well as more experimental swings (Get Out, Split) on extremely tight budgets (typically 5 million or less for a non-sequel). It's okay if a few of the swings strike out, because the financial risk is so low; it helps justify the sort of out-of-the-box creative risk-taking most studios avoid. You also have to keep in mind that they produce many films on that $5 mil scale that never see theatrical distribution; they'll instead be pushed out as a direct to TV release (often through HBO) or direct to DVD/VOD (i.e. the forthcoming Stephanie). If Universal isn't interested in giving it the full marketing push, i.e. with Upgrade, they'll occasionally hedge their bets and release it themselves through BH Tilt. It's a fairly complex but well-oiled beast.
Illumination does build animated "blockbusters" on a relatively cheap scale - as you said, $80 mil is nothing when a typical Pixar or even Dreamworks film runs from $150-200 mil - but that's not an insignificant amount of money. Their films still have to be major successes (i.e. $400 mil+ total WW gross) to get into the black, especially when half the spend (or more!) comes down to the already-discussed, all-in marketing. In other words, even though the initial spend is lower, they still can't really fail. Lucky for Illumination, they've yet to have a real commercial failure (Hop notwithstanding); sooner or later, I think they will, as they've yet to develop a franchise with the pull of Despicable Me. (Sing and Secret Life of Pets performed fine and extremely well, respectively, in their initial debuts, but I believe prospective sequels will suffer due to the preceding films' lacking quality.) There's a reason they're leaning into Grinch and Super Mario - they're reliable, "too big to fail" brands.