I had exact same worries about road bikes ‘strength’ when I got into it about a year ago.
I built up and ride a 40yr old 531 lugged steel frame with very expensive 60s hubs + 80s rims which I’m always worried about buckling….
however. Put nearly 1000 miles on it now, first 250 of that mostly on gravel tracks & rutted broken tarmac with monster holes in it, with 15kg of panniers on the back.
Nothing has moved, frame is fine, rims haven’t budged 0.5mm, nothing, nada. And I am what I would call ‘heavy’ on bikes (not me, only 80kg, but i ride lazy).
a budget road bike is going to have its short comings, but frankly for commuting, where its going to be left out, banged into, thrown around, lock chain gouged into it, ridden in the rain, sleet, salt and filth (and then not dried or cleaned afterwards), cheap, is what you want.
When you get it, throw some ‘Refuse’ tyres on it, (maxxis or swalbe) around the 28c sort of size, and then enjoy throwing it down canal paths, potholed tarmac etc.