Big fan of retro (boomer shooters). Is this worth getting? Is this game a lot like Amid Evil?

I dont like secret hunting, but I noticed that runes are given even without secrets. If I ignore secrets and just play the game without hunting for them. Will I at the end of the game have all runes?

Does it require to boot up steam client to play it?

What's with the steep drop between the overall positive reviews (88%) vs the recent ones (61%)? What's the more realistic score?

So I finally got around to completing this game, but the last boss was a nuisance. All of his attacks were easy to dodge, all but one, where he does a horizontal slice that covers the entire arena. I tried jumping over it, dodging through it and everything else I could think of, but it seems there's no legitimate way to avoid the attack. I ended up winning by simply tanking through those attacks while blasting him with everything I had. It took four attempts to do it, simply because that swipe attack, ...