My first race was Thanksgiving 1983, so can't really comment on what it was like during the first running boom of the 70's. But I raced a ton 1983-1993 (25-50+ races/year) and less 1994-1998 but still 8-10 races a year those years so I'll give you my take from when I was active racing compared to today. These days I produce road races...
I wouldn't describe the feeling in those years as a "big dang deal", but it definitely was different than now in a big way. Average finish times were certainly a lot faster then, that change seemed to take place in the early-mid 1990's where I live. The fast local guys raced, on average, a whole lot more than they do now. Same with the 2nd and 3rd tier locals, guys more in my range (I was 3rd tier local at best!). Fast women weren't unheard of, but I would say women's depth up front is deeper now, at least where I live. When I look at local results, the real top end open guys I see in a few results a year. It's almost like "oh look, so and so raced this week" and that's noteworthy. BITD it seemed like I saw those guys every week at a local race.
Part of that is of course the entry fees. 1987-1988, first year and a half I was out of college, I did about 65 races (running, Nordic, bike races, even a couple tri's in 1988), and I don't think I spent $300 total on entry fees. Boston Marathon was expensive (haha), I think it cost $18 and you had to buy a TAC membership for $12. Club races were $2-$5, maybe a couple were $8-$10. The local tri's I did were only about $25. Today the club races are still there (and inexpensive where I live), but the "regular old road races" are all $25 and up. I'd have trouble justifying $1000/year to race as much as I used to.
Here's another pricing example... A local XC ski area has had a summer XC racing series for about 20-25 years. Very informal, no big party at the finish just show up, race, head home. This started out as I think $2. This summer they're $12/week. The funny thing is, when they started they were getting 30-50 people/week. This summer they seem to be down a little in numbers, 175-200 most weeks, but most recent years they've been 225-250 every week.
Another thing I saw change was BITD there were a handful of local races that sort of "owned" their spot on the local/State calendar and nobody else put on a race the same day. Or maybe it was just that we didn't have the google to look up what races were happening and we all knew the races that were going to have good competition and be run decently so that's where we showed up. Today you still get that, around here, to a degree. But other weekends there will be 5-6 races happening (small city, ~40K people). When that happens it seems like the quicker locals end up at different races and the competition is greatly watered down.
Depth of competition is probably the thing that is most noticeable to me now, but fast times are still fast times. There are a few local races that are mostly the same now as when I was racing. Stowe 8 Miler is an example. They moved the start/finish, but it's the same loop. My best time on that course was just over 48 minutes, and that got me barely midpack. Late 1980's, decent size field. This year, I think a slightly bigger number of finishers (496), but 48:10 would have gotten 7th overall. Same with the local 5k's, I was pretty consistently mid to high 17's and usually well back in the results. Winning times today are often not that far off what they used to be, but the times I was running would be way up there now.
While I think it's great that more slower people are willing to come out to races now, I do miss what races used to be. Overall, to have people taking part in races even if they're running super slow or walking, I can't help but think that's good from a fitness and motivational standpoint.