Of course, if agents arrive in a van fully armed, preferably with AK-74 from a weapon box , there is a 80% chance to complete a mission flawlessly.
Not always, and less so as time goes on. Going after e.g. a cult outpost with just a van and AKs highly depends on your tactical acumen, and assaulting a base, a bad zombie mission or a horde of Chupacabras is tilted against you quite a bit. You should move on from vans and AKs as soon as possible, within the first half a year or so.
But it's no a tactical level. There is no chance for a beginner to know in advance what to research: how useful are dogs? How good is a hunting rifle? Should I research a lab instead etc.
You should
always aim for better research labs, that's not something unique to X-Com.
Dogs and melee are not something you'll think of as OP when you see them first, I'll grant you.
Bad equipment can be compensated with better tactical play. Since you have trouble with that, I assume you're not good enough to kill half a dozen cryptids with a pocket knife, so you need to stack the deck in your favour on the strategic level.
But if you're not good at completing moderately tough missions and skip them, your strategic position will deteriorate, up to and including manors all over the place and/or a score death.
So if a player botchers half of early missions, he's still be OK?
Depends on which missions and how your score is doing otherwise. In general, if you do badly at the start of any strategy game, it'll snowball (and success will also snowball). We've had a few people come in and complain about losing in a year or two due to score/manors.
If your goals are doing well without the missions, the latter are skippable. But I get the idea that you don't really know
what your goals are, yet.
It's pretty boring since there are a lot of cult apprehensive missions. I wonder if I'm playing the game a wrong way?
Kinda yes. Research the cult dudes to open up new missions to capture new cultists to open up new missions and so on. Cult apprehensions should be gone or largely gone around the second half of '97.