Well, that's only half true, because the price range of the current mid-fi gear occupies the range where the summit-fi was 10 years ago. Also, now the price disparity between the different segments is greater than ever. What used to be something like: entry-level at sub-$50, lower mid-fi at $50-150, upper mid-fi at $150-250 and TOTL at $250-500 has turned into something like: entry-level at sub-$100, lower mid-fi at $100-400, upper mid-fi at $400-800, lower high-end at $800-1200 and TOTL at $1200-5000.
As someone who has heard a lot of the TOTL gear from before - sennheiser ie8, shure se535, etymotic er4s, westone 4, ath ck10, etc. I can only half agree with the statement that the mid-fi iems of today sound better than all of the top-tier iems of yesteryear. It's definitely not just the tone - detail monsters like the ety er4s and the ath ck10 (and most TWFK-based iems of before) are still detail monsters. Yeah, with the evolution of hybrid designs and BA drivers some of the newer iems might have better low-end or bigger soundstage, better layering, etc. on top of the good details, for instance like the flc8 introduced a marriage between a TWFK and a dynamic driver for the bass.
For me the chi-fi divers used in most of the mid-fi stuff nowadays still can't touch a single TWFK in performance and that's the issue - now we have manufacturers using 6,8,10... 42 drivers trying to win the numbers game while in reality there are far superior 2-3 driver iems out there. In fact, I still stand by my opinion that the closest to an upgrade to something with a TWFK like a brainwavz b2 or ath c10 I've heard is the Noble 4 (now Savanna) and that's a $500 iem, so I wouldn't go as far as saying that all of the current mid-fi stuff (if we're talking $100-250 iems) is better than the old flagships. Some of them are, but mainly because even back there there was stuff like the sennheiser and shure products trying to pass for flagships and being way too overpriced for what they were. With, that said, we do have more versatile iems now and we can get something with good details and good bass for less money - it might not excel in detail retrieval as an ety er4s, but it will have better low-end and pretty good details for cheaper.
The main segment that has really changed is the entry level. Before, there wasn't much choice and there weren't many good sub-$50 iems, but with the progress of chi-fi now we have cheap stuff that is blurring the line between entry- and mid-fi. Also, due to the insane competition more expensive top performers in the mid-fi range of yesterday like gr07, re400, dunu titan 1, etc. can be found at half (and even less) of what they used to sell for.
The times are surely crazy, but I urge people to try to not jump on every hype train and if possible to wait for someone with more experience to chime in before jumping on. It just seems that there are way too many people who don't have proper point of reference when they are recommending the new giantslaying stuff and then a month later comes along the yet another giant slayer and the cycle continues. This advice is especially aimed at people who don't have spare money to burn for monthly experiments. If you only have $50, $100 or whatever amount of money to buy a new product and don't intend to spend such an amount on monthly or even weekly basis, then do your research and get something tried and proven rather than being swayed by the current hype train, which will never return once leaving the station.