As long as you do auto-switching in an auto-switching pool, it's okay, why? You will always have a Full Share to that mining pool even when they switch to other algorithms, because all of the switching processes handled by that mining pool.
But then, as you said, peoples including auto-switching pool have an almost same variable for counting profitable coins. Current price, Difficulty, Network Hashrate and so on. What does it mean? Peoples will be pointing to the same coin, and it will increase Network Hashrate which will affect the difficulty. And profitability will cut-off.
Some Old-Miner may be doing something different. Sometimes they do a Solo-Mining with new coins, but of course, they have own calculation method with that. Sometimes they mine the solid coins and hold it for a few time. And many more.
Personally, I didn't do auto-switching. I have a few rig for solid coins and the other rig doing high mobility mining (didn't mean I'm the Old Miner. lol)
OK, yes your first point does make sense, and that's why I do often use switching at miningpoolhub.com but it's usually just one algorithm that switches between a few coins, which has most recently been equihash, but then I noticed in the last week that the price of ZCL completely fell off a cliff, but the equihash auto switch kept switching to ZCL, even though it had dropped from over $100 to around $10. It didn't make any sense to me, but maybe the difficulty dropped so much as the price dropped that it was still worth it.... There is so much going on in the background between miners, pools and exchanges - and there are so many changes, forks & shitcoins to get distracted by!
This is really a hobby and a challenge to me that also happens to make money sometimes but I don't have the time to keep up with what is the best way anymore.
I have solo mined a few new coins. I solo mined a few NXS blocks when it was worth about $0.40. Now though it seems that the latest thing that happens is that the earliest people to a coin are starting masternodes. There are just way too many neoscrypt based DASH clones out there and the newest ones have like 20-100 masternodes which must belong to the devs, and I think they look like they are mostly scams.
I wouldn't call myself an old miner either - when I started I was buying used equipment from people who were mining litecoin in 2014. If they HODLed that LTC they must be rich now!