A few of things, OP:
- A "regional university" isn't really a thing. Academic jobs are usually classified by their Carnegie classification, which would be R1 (huge doctoral research school), R2, Doctoral Institution, Master's Institution, and so on...
- Professor jobs usually have pretty different expectations based on the institution's Carnegie classification but also on the field. At an R1 you're going to need to get mega-grants and publish, whereas at a Teaching Institution you may not need to engage in a lot of scholarship, especially if you're not on the tenure track. In Organic Chemistry you're gonna need to be getting grants, spending time in a lab, using more grad students, and publishing more, whereas if you are teaching Architecture you might present at conferences and maybe keep a small practice to fulfill your scholarship component. Furthermore, there are tenure-track jobs and non tenure-track jobs (many of which do have promotion and security), and there are different expectations for those, too. All are hard to get, but the point is there are 1,000 types of full-time academics.
- At even the not very selective schools (90% acceptance rate or more) there are going to be VERY good students. At the higher-achieving levels (research assistants, TAs, mentoring honors student thesis projects, etc...) these are the students you usually connect with. As programs progress, students often grow into their field. I teach at one of these schools and I could name a dozen kids right now who could absolutely hold their own against Hannah from Yale and Henry from Dartmouth.
- A common misconception is that less prestigious schools are filled with idiots who are just there to party. Maybe some, but these schools provide a really important place for many first-generation and otherwise disadvantaged students to achieve higher education. If after a year students are really not ready and can't figure it out, they often leave on their own.
- I think a lot of people picture professors in tweed blazers waxing poetic in the bottom of a captivated lecture pit all day long, and I guess some of us do that sometimes, but teaching can actually be a really small part of the job for many of us. Furthermore, reaching and engaging students who aren't already top of the heap is incredibly rewarding, and this is often WHY we do it for those of us who really do enjoy the teaching part.
TL/DR: No, it's not frustrating at all. I've taught at both types of institutions, and what impacts me the most in terms of job satisfaction is how much I'm expected to produce and how much control I have over my own schedule (better at a "bottom tier school" for me), how rewarding my work is, which is directly correlated to how much I feel like I am helping people (better at a "bottom tier school" for me), and the sense of community among my students and colleagues (also better at a "bottom tier school for me").